According to IGN, Dinosaur Planet is a lock to appear on Gamecube.
While not confirmed by Rare yet, "sources" are saying that Dinosaur Planet was scheduled to becoming a Gamecube title around November of last year, undoubtedly to help pad Nintendo's launch lineup.
No word yet on if the rumors are true, and Nintendo is pushing Rare to turn Dinosaur Planet into a "StarFox" title.