Wandering Son/WMG

Nitori is a lesbian and Takatsuki is straight
She's only ever shown interest in girls. She sees Takatsuki as a boy, but it's very debatable that she mistook her feelings for love when it wasn't actual attraction. The manga does like showing different shades of stuff, so I wouldn't think twice about it having one gay Transsexual and one straight one (Yuki for straight, and maybe Takatsuki unless he's gay or bi). Speaking of Takatsuki, it's even more debatable with him since he hasn't really appeared to like anyone so far. He did seem to like Yuki at first, though that may be a case of "I passed?" rather then him liking the fact a lady hit on him. He apparently could have liked his male middle school teacher, but that appears to be confusion rather then a real crush.

Nitori and Takatsuki will trade first names
It's been lampshaded several times, and discussed several times. It doesn't seem they've taken much thought into name changes, and there's really few ways to make "Shuuichi" into a girls name ("Yoshino" can change into various things though).

Saorin is going to do something to make Takatsuki uncomfortable again, and accidentally push him towards medically transitioning.
We saw that when she told Takatsuki that she liked his hair long, and that boys could have long hair too, he grew it out because it made him feel validated as a man. When Yama-p confessed his love, Saorin said that Takatsuki was a normal girl, and that the way he was he was very pretty and it would only get worse, which pissed off Takatsuki so much that he cut his hair off again to avoid people thinking of him as a girl anymore. Saorin is probably going to say something like "You're a pretty girl/You won't grow more/You're getting even more feminine everyday." This will trigger an alarm that makes Takatsuki act.