Yeah, no Marvel or Star Wars. Those aren't actual Disney properties... Disney just acquired them LONG after they were already well known and established.
I'd like to see Pixar character incorporated, though I still want to see the classic animated characters in there as well.
It would be cool if they could do something that appeals to multiple generations. Have some of the more recent stuff in there as far as movies and cartoon shows go (Wreck it Ralph would be a no brainer), but go back into the history as well.
I wouldn't mind seeing something based on DuckTales. Heck, since they technically shared the same universe, they could easily make a single planet based on DuckTales and Darkwing Duck. I'd love to see a summon involving Gizmo Duck!
It might get a bit too "meta," but I actually wouldn't mind if they found a way to have worlds based on different versions/continuities of the same characters, and then have those different versions interact and cross over. Perhaps have the more traditional incarnations of Chip & Dale and then have the Rescue Ranger versions... or have the characters from the Jungle Book and their Tale Spin incarnations as well.
Perhaps in addition to different worlds, they could also introduce other dimensions as a way to explain something like this, and have an alternate version of each world (or at least several of them) or something.
At any rate, I'd love it if they could expand the scope of the game. Not that KH 1 and 2 were small in scope by any means, but they could REALLY go all out with this one and make it twice as big or more.
It would even be cool if they could incorporate things from Disney theme park attractions (but again ones that are either original to the parks or are based on Disney properties... nothing Star Wars related, etc.).