Lucario is, I think, the most likely Pokemon to make it into Brawl. Of course there are going to be new Pokemon; let's not kid ourselves, it's one of Nintendo's biggest franchises. Lucario is probably the most recognizable Pokemon of the 4th generation, he fits in perfectly, he has his own movie, which DOES matter, and he seems like he's going to be an icon of the 4th gen for years to come (see kaid's Lucario thread for more about that). He's very likely, IMO.
Lucario's Chances: 82 %
Nominations:
3x Midna
2x Happy Mask Salesman (Has Gamefaqs done this guy?)