Well I have no theories at all.

All I would want in it is:

A lot of Disney, like in the other two.
Sora, and the king.
Riku and Kiari I guess could be in it.
Malificent of course! The best villain in KH 1 and 2!

And most importantly, Donald and Goofy on your team, if they dont have them on your team, or not in a big part of the game, is there any point in buying KHIII?