Puella Magi Oriko Magica/WMG

Oriko is
Because the piece of promotional artwork marks her as a Token Loli, and she's seen with Mami and Kyoko.
 * Another thing. Homura is mentioned to be appearing in the series. Since it seems unlikely that Oriko will take place in the week between the beginning of Homura's Groundhog Day Loop and when Homura transfers to Madoka's school, it's possible that we will see Homura in the hospital, before the loop begins. A likely reason we would see her there is because Oriko is an Ill Girl too, and they're in the same hospital.
 * Oriko is not the girl with pigtails from the promotional art, but that girl could still be.
 * Homura boldly kept
 * We may actually have a piece of evidence for this: Remember the runes in Episode 3? The one that basically went The line before that one is apparently the origin of Homura's Fan Nickname Homuhomu. Now remember the following:
 * Should be mentioned that if Oriko does call Homura Homuhomu it would still fit with her "people don't usually call me by my first name" statement in episode 10.
 * The above speculation was written when it was thought that Oriko would be a Prequel. Now it's unknown when it will take place, although this doesn't necessarily invalidate any of the speculation. Flashbacks are always possible.
 * Preview pages of Oriko have been revealed, and it looks like we've been trolled, the girl on the cover is NOT Oriko. In that sense, this theory is Jossed, but...
 * Jossed. Mami fights Charlotte in the manga.

Yuma is
See above, and replace "Oriko" with "girl on the cover".
 * Jossed.
 * Jossed.

Similarly, the girl on the left in the second cover is
Based on nothing more than the similarity of their uniforms.
 * For the record, a larger image of the cover has surfaced, and we now know the girl on the left is Kirika.
 * Jossed.

Oriko, the real Oriko, not the girl we thought was Oriko, is either
Again, minor visual details. The former is probably more likely.

Oriko Magica will, through whatever fashion, show us
Because why not? They teased us with their silhouettes at the end of the anime.
 * For the record, that girl has been revealed as Oriko.
 * Jossed.

Addiing on to this, Oriko Magica will show us
Because why not?
 * Jossed.

Oriko Magica will take place in the fourth timeline of episode 10
An official description of the second volume calls it "The story of a passed time line".
 * Jossed. It is a passed timeline, but not one we've seen before.

Oriko will become
In the preview pages, Oriko is looking at This is very similar to the scene Madoka saw in the first episode.
 * It's not said that that's the witch she will become. She appears to believes it's a witch she's destined to encounter
 * The biggest problem is that is said to have been around for a long time.
 * Then again, it's said that.

Either Kirika or Oriko will become
One word:
 * Here's something to ponder. Oriko means "sewing lady" or "weaver girl". Based off the fact that she can apparently see the future, the inference might be "weaving the threads of fate". Now,

In the anime, Yuma
The writer of this WMG admits that at this point, stuff is being thrown at the wall to see what sticks.

Yuma is Doomed by Canon.
Come on...this is a story of a "past timeline," and in the anime, Yuma is nowhere to be found and there is no reference to her. She's goin' down.
 * It's possible she survives
 * Jossed, at least in the Oriko timeline.
 * Jossed, at least in the Oriko timeline.

Oriko is manipulating Kyubey to her own evil ends.
At least, that's the impression I got from the first chapter.
 * Confirmed.

Oriko's prediction of Walpurgis Night occurs in all timelines
This is how Mami knew Walpurgis Night was coming in the first timeline of episode 10; Oriko told Kyubey, who told Mami. What she saw next and what drives her future actions are entirely dependent on Homura, who is acting as a Butterfly Effect; her actions and changing goals alter Oriko's other predictions in each timeline, which is why there were no magical girl killings seen in the anime.
 * Oriko never predicted Walpurgis. She predicted She may still have contracted, seen this and mentioned it other magical girls, but it's unlikely from Homura's comments that the timeline is irregular and the fact that.

Even if magical girl killings did occur in alternate timelines,
It's very likely that Oriko and Kirika are trying to pre-emptively stop the creation of Walpurgis Night. Which means that

Madoka still dies or worse in the end.
So that Homura goes back. Also, it is in such as way that Homura attempting this method in later timelines; ie, getting to Madoka first, is no longer an option. Possibly by bombing Oriko's and Kirika's houses every timeline from here on. This gives Kyubey and Mami time to get to Madoka. But the alternative is worse.

This is all one of Homura's plans
One of the problems Homura has run into is that she needs to get close to Madoka to protect her from Kyuubey, but getting close to Madoka in itself at the very least makes her sacrifice herself to stop Walpurgisnacht, if not run into witches earlier. So Homura decided to have that weird oracle girl take care of all of the magical stuff for her. Not to mention that having one of the main heroes on the other side makes for good drama.
 * Jossed. Homura had no idea what was going on until

Oriko
An oracle didn't just tell the future - they also communed with the gods.

Homura not caring about anyone but Madoka will come back to bite her in the ass.
How? Two words: Sayaka Miki. Poor girl cannot catch a break; why should here be any different? Homura will be so focused on keeping Madoka safe that she won't pay attention to what Miki's doing until she goes all magical girl on her, and that will end... badly. And that, of course, will be what brings Madoka back into the mix this time...
 * Homura is part of Madoka's social circle this time. This is the timeline she's least likely to miss something like Sayaka hanging out with Kyuubey.
 * Sort-of confirmed.

Kirika isn't actually killing magical girls
She's just killing their bodies. A truly dead magical girl reverts to their civilian outfit, which her victims haven't.

Following from this, Yuma is important to Oriko's plans because she'll be able to revive everyone after it's all over.
 * Or it's worse: Kirika is stealing their Soul Gems, and Oriko has a way to turn them into Grief Seeds.
 * Kirika could be stealing their Soul Gems to prevent them from becoming witches, and Oriko might be collecting them thinking it's better this way...
 * The Yuma part is Jossed.

Kirika and Oriko are going to erase themselves from the timeline somehow in whatever they're doing.
This is in order to set into motion the sequence of events where Homura and Madoka interact such that the Walpurgisnacht will be defeatable. ("saving the world.")
 * Or perhaps Oriko is foreseeing even past that, seeing Madoka's capacity to change the entire system; but she'll need to create a schism between Homura and Madoka's friends.

Madoka is going to remain uncontracted in this timeline.
But Homura will still have to rewind because
 * Confirmed.

Oriko Magica will have an Animated Adaptation
There will be an epilogue explaining

After
Instead, she gives Mami, Kyouko, Yuma and herself time to
 * This might be canon; Homura might only be able to rewrite time after/during Walpurgisnacht.
 * No, Homura rewinds time as soon as Madoka dies or becomes a witch; she doesn't even have a choice in the matter, in that it happens automatically. Otherwise, she's acting outside of her wish. But since the timelines she leaves behind persist in their existence after she leaves them, everyone can still hate Kyubey.
 * Gen Urobuchi has stated that Homura has to wait a whole month before she can use her time travel ability again. Fortunately, the previous world is not erased by Homura but continues to exist alongside the next world as a parallel world.
 * ...Fortunately? If that's true, and it applies to all timelines, then it means that Homura's influence essentially led to a huge amount of destruction across many worlds, especially the ones in which Madoka became Kremhild Gretchen, none of which was actually "reset".
 * Presumably this was fixed by Madoka's wish; which apparently bypasses the "time travel creates an Alternate Universe" scenario.
 * Though this timeline is actually pretty well off. There are at least three Puella Magi left to fight Walpurgisnacht, one of which having healing powers so death is unlikely, and corruption is also unlikely as in the first chapter, Kyouko stated that she had more Grief Seeds than she could use alone. Madoka is dead so she can't become Gretchen. And with the three Puella Magi learning and coming in terms with their fate but still determined to fight on, they'll probably do whatever they can to prevent Kyubey from contracting others. So hey, maybe Oriko did at least save this timeline.
 * As of the end of the anime, Walpurgisnacht did not ever exist, so there is no threat to the world. In fact most of this manga events (besides the same people becoming magical girls) probably never happened, because they retroactively had no reason to happen. As about beating on Kyubey, well, he remained unharmed when the Earth was eaten by Krimhild Gretchen and then at least the Milky Way and surrounding region of space blown up by Madoka. True form of "hardware" on which his consciousness actually runs is probably beyond human imagination, and spending effort on destroying drone bodies of his pre-retcon self only plays into his hand.

There are no magical-girl killings in the canon timeline...
.., because Oriko foresaw not the end of the world, but So she decided not to kill magical girls, but rather let them all live so that the future she saw would happen.
 * It would explain Oriko's and Kirika's absence in the last timeline of the anime. She would not want to risk the Golden Ending by getting herself involved.
 * But where were they in the other timelines?
 * Explaining their non-appearence in timeline three is easy: Walpurgisnacht is defeated and Madoka's request for a Mercy Kill prevents Kriemhild Gretchen's existence and the need to intervene. The other timelines are less explainable (we do not know which KG was the first unstoppable global threat), especially timeline four makes little sense.
 * Incorrect. Oriko's wish was to  not to see the future. For all we know, in an alternate timeline, she instead saw herself becoming a witch...
 * Her wish resulted in her oracle ability. The powers that come with wishes tend to subsume them.

Margot is the witch name of
This page shows a sign that reads "Margot(unreadable) Garde(unreadable)", probably the witch's name and her "garden", which is lined with roses. It points into the center of her barrier, where she are waiting.

Everything happened exactly as Kyubey wanted.
Oriko believed that contacting Madoka was a top priority to him, that's why she engineered most of the plot... but Kyubey wasn't too fast to  even though he was implied to know about Oriko's scheme far before taking any actions (considering his ability to read thoughts, anything else would have been surprising, really). When Oriko's plan actually was put into motion, Kyubey. Instead, he went to watch the fight. He didn't care when, offering no real comments, and treating this event as completely insignificant to him. Most likely (due to being, again, a telepath), he knew very well what Homura is up to. His main goal was forcing Homura to rewind time again, sending her on another cycle of supercharging eventual ultimate-timeline Madoka, and his secondary goal was destroying Oriko, just because he eliminates magical girls who dare to plot against him (and aren't useful to him) on principle. Note, that the final confrontation as it actually happened would have fulfilled both of these goals with any realistic outcome.
 * That makes no sense in Puella Magi Madoka Magica Kyubey didn't know Homura was a timetraveller until she killed him with bullets before he could contract Madoka. He can't read thoughts he can communicate telepathically. There is a difference.