Okay, let me say something I said on the Gamefaqs boards, and please don't get upset:
NO, JUST BECAUSE A CHARACTER DOES NOT APPEAR DOES NOT THEY WERE NOT SUBMITTED OR THAT SAKURAI DOESN'T LIKE THEM. IT ALSO DOESN'T MEAN THEY ARE ALREADY IN THE GAME OR PLANNED FOR THE GAME.
...anyways, Stafy is pretty similar to Kirby, but I think he'd still offer something unique that the development team wouldn't mind including the game. I've noticed that Melee took a turn away from "major stars" towards "humanoid" and "mature" characters. Rather than going with the Stafy type characters, they stuck with doing ones that were either very human or humanoid, and weren't necessarily discouraging to older players (because, though I feel otherwise, there are a lot of people who play Melee who would be really upset if the roster wasn't a bunch of Star Fox, Zelda, Metroid, and F-Zero characters. You know, the more "serious" ones).
Brawl so far hasn't shed the Melee philosophy, but we're not that far along in our knowledge of the game, so it could change. Who knows. They obviously "upgraded" Pit, so they could easily do the same with others. I just hope they do become more inventive and care more about the game and not the appeal, like they did the original. I WANT to see Stafy, Demiru, Sukapon, etc. Sure, Falco and Ganondorf are cool, but I could've done without them. Definitely. But losing the opportunity for a fighter as cool and unique as Lucario? Unheard of.