I did hear the Donkey Kong Island name somewhere, I think it was a rumor post on the PGC ezBoard before it was closed, supposedly a kick-back to the DK Country games and style, instead of DK64, even up to the fact that it's 2.5D. Still a rumor, but sounds like a likely one. As for HAL doing it, though, I'm not sure. Then again, NCL could've been impessed by the "Adventure" 2.5D action stages in Melee...
HAL could be doing that, or it could be something quite different. I don't think their next game is a Smash Bros., although I can't wait for a new one.
Here's a weird one, somewhere along the line, on an official release list, Kirby's Air Ride showed up again. Yes, the game that's been in developmental hell since the EARLY N64 days showed up on one of the more recent "title lists" from Nintendo for Gamecube, it's possibly the one where Nintendo of Europe leaked the 2003 titles. Maybe IGN still considers that secret, if it's right...