Okay, this was bound to happen eventually. Here's a KHII thread.
I'll list rumors that people hear and confirmed truths. Also just talk about it and whatever... Yeah.

Rumors:
blonde-haired kid in screenshots is playable (75% certain)
Vincent Valentine will star in it (Unknown)
Blonde haired kid is Tidus (0% certain, very very unlikely)

Confirmed
You fight Hades alongside Auron
King Mickey will be in this game.
The cloaked person is in a group called the Thirteenth Order.
The blonde kid uses the twin blades Oblivion and OathKeeper.
Red haired dudes name is Axel
New enemies called Nobodys
Blonde haired kid fights big white monster in dream
Ansems baaaaaack.....
4 confirmed worlds: Hollow Bastion, Hercules, Beauty and the Beast, Twilight Town
Custom Keychain (Details unknown, but basically attacking, defending, or magic)