Real Steel/WMG

All the robotic fighters are sentient, to an extent
While it appears that most of them are controlled via their owners, their ability to learn showcases that their AI slowly evolves over time and they start to become self aware.
 * So in a way kinda like Warjacks

"Farra Lemkova" my ass....
Excella, what are you doing here??

Atom was an early prototype for Zeus.
I honestly expected this to be revealed near the end. The eagerness of Zeus' owners to buy Atom made me feel that they knew something that Charlie and Max didn't. It was stated that Atom was considered an unusual Generation 2, and he was very good at adapting (which was also Zeus' specialty). My guess is that they didn't expect anyone to find an old prototype, and didn't want the technology getting out. Certainly, they never expected a pro-boxer to turn the prototype into something capable of going toe-to-toe with the latest version, though... This could actually fit quite well with the idea that Zeus' designer had been in retirement. It also give some extra weight to the final fight, as Atom represents a more basic design, that he had abandoned in favor of going bigger and flashier. He was literally having his mistake pounded to bits by his abandoned greatest creation.
 * Must be noted that one purpose of a sparring unit would be to accustom a fighter to its opponent's moves, meaning that the unit would have to pick up those moves and execute them perfectly and be able to do so with enough time left over for meaningful training. Insane adaptability is a pre-requisite for that.
 * However, that doesn't mean Zeus' designer might not have made that system into Atom as a prototype for Zeus' opperating system. He's regarded as one of the biggest names in robot design, so it wouldn't be a stretch to imagine he'd made a sparring robot with that system and then been inspired to make a better one for Zeus, one that didn't just copy moves but adapted to them, overlooking the natural advantage of a robot being able to replicate human fighting style.

Atom's success will begin a major renovation of the sport, with many former human boxers now being brought in to "train" the robots
This means Charlie and Max escentually re-employed thousands of people singlehandedly. If this turns out to be true, this would be awesome!

The name Zeus was a subtle reference to Rocky
He played the same role as Apollo Creed, and shared a name with the mythological father of Apollo.
 * Pro wrestler Hulk Hogan made a movie called "No Holds Barred" in which his big fight was against an enormous scary guy called "Zeus".

The sequel has Charlie going full-time into training boxing robots, while Max's aunt and uncle invest in a robot boxing team so Max can get into developing boxing robots professionally...
which means that the next Real Steel tournament leads up to Charlie and Max FACING EACH OTHER.
 * And Charlie activates the shadow function earlier this time, leading to Max (who got to keep Atom) getting into the action and turning his bot into a Dance Battler.

Atom's popularity is gradually destroying big-League boxing
Lemkova gave no sign of actually thinking Atom was a threat to Zeus, so why the 200-grand offer? Answer: Atom's popularity is drawing attention to the small-time independent fight circuit, and people are discovering the entertainment value is about the same at a much lower ticket price. Lemkova doesn't want the competition, so she tries to pull Atom out of the equation so people will come back to her overpriced and probably-rigged productions.

The sequel will have a theme of escalation.

 * The film mentions that people always wanted bigger bots, bigger fights, and bigger violence from the sport. In the sequel even the official sport will start abandoning many of the rules as they become officially sanctioned death-matches. The fights will also be bigger, with tag-team matches and multiple bots in "King of the Mountain" type fights.