There is a rumor going around that Square-Enix has made a deal with Nintendo to license a character/characters to Nintendo for secret unannounced project. Apparently the characters going to be used in the game are some who haven't been touched on in a very long time.
My early guess would be some characters from Chrono Trigger being used in the next Smash Brothers game. I can't think of any other noteworthy game besides Final Fantasy that Nintendo would want to use characters from. I also don't think it would be Cloud since he has been featured a lot over the years in other Final Fantasy VII spin-offs. Would a Chrono Trigger sequel be too far fetched?