I am hopeful because I just read in in the April issue of a gaming magazine (I can't remember which one right this second) that Nintendo and Square Enix are working on a Wii exclusive game: Mushroom Kingdom Hearts.
Yes, I realise that it's probably a fake, since this magazine is also the same one that said Sonic and Tails were in SSBM, but hey, the art they created/recieved looks pretty official to me. I may scan it in here in the near future.