I had mentioned it before early on, on some forum board but I said I bet there is going to be 3rd party characters because the SEGA was dropped from the title. So far Danica Patrick, and Wreck it Ralph are the 2 outside characters. I'm really thinking a Nintendo character will be present on the Wii version.
I made the beat http://www.youtube.com/watch?v=Qmv-3Jp7Tl4&feature=channel_page
It has been said that Vectorman is NOT playable. Please keep in mind that the decisions for this game are mostly made in Japan and Europe, where Vectorman was never all that popular (neither region got Vectorman 2 from what i remember). Also, while there seems to be a recent obsession with Vectorman, i think it's fair to include franchises that have more then 2 entries and are currently more vital over Vectorman.
Axel & Blaze
Well, they are already showing some beat'em up love with the inclusion of Gillius from Golden Axe and they hinted at cars with more then one driver, so i think this is possible.
, and Ristar in this.
Ristar had a little cameo on one of tracks of the previous game, so i think his inclusion is likely. However, while i like Ristar, it's still just ONE Genesis game, so i wouldn't get worked up if he was left out in favour of characters from longer series like Wonder Boy, Puyo Puyo, Ecco, Die Hard Arcade/Dynamite Cop, Phantasy Star or Panzer Dragoon.
Also, would be nice to see the Crazy Taxi gang
B.D. Joe has been confirmed as a returning character.
and a return of Jacky & Akira (hopefully Pai and Sarah join them).
Virtua Fighter definitely deserves representation, i think they'll return.