I doubt we'll get a "new" character to be honest, we got Toon Link in Brawl, and I doubt they'd put a new character in, if they do, who? - would be the question. I don't think there is a character important enough to be included in the roster, I think they might go with a character from the newest installment, Skyward Sword.
However, I'd bet on them including a new stage or maybe a new trophy from the game, just to acknowledge it's release. Of course, we already got the the Great Sea stage in Brawl, so I think another one won't hurt. I'd like to see a stage set within the Forsaken Fortress to be perfectly honest.