Here are some highly possible characters and why they are so:
Nintendo Characters:
Little Mac (Punch-Out!!) - Factors contributing to his inclusion: Face of a Nintendo franchise, Nostalgia factor, a boxer would fit into Brawl extremely well, a boxing ring would work well as a brawl stage. Little Mac's could have his trademark star-uppercut as a special move.
Professor Hector (Gyromite) - Factors contributing to his inclusion: Face of a Nintendo franchise, Nostalgia factor, could include ROB as a special weapon/feature. Dynamite seems like an obvious weapon for him as well.
Captain Olimar (Pikmin) - Factors contributing to his inclusion: Face of a Nintendo franchise, could include creative gameplay mechanics with Pikmin.
Mii (Wii Sports) - Factors contributing to his inclusion: Promotion of Nintendo's Mii Channel, it would be reall cool to be able to play as yourself in Smash Brothers, cool weapons - bowling ball, boxing gloves, baseball bat, etc.
That said, I expect far more than 4 new characters. However, I highly expect these four. Professor Hector is the only I wouldn't be terribly surprised to see omitted.
Third Party Characters
Bonk - Factors contributing to his inclusion: He's the icon of a third party (Hudson), Nintendo has a great relationship with Hudson (see Virtual Console), Nostalgia. A Dinosaur land stage would work well.
Mega Man - Factors contributing to his inclusion: He's the icon of a third party (Capcom), Nintendo has a great relationship with Capcom (GBA Zelda titles, long history of 3rd Party support), Nostalgia.
Pac-Man - Factors contributing to his inclusion: He's the icon of a third party (Namco), Nintendo has a great relationship with Namco (Mario Kart GP, Star Fox Assault, etc.), Nostalgia. I do question what sorts of moves he would have.
Sonic - Factors contributing to his inclusion: He's the icon of a third party (Sega) and arguably the second biggest icon in video games (afte Mario), Nintendo has a great relationship with Sega (F-Zero GX, Mario & Sonic at the Olympics), long-time rivals, Nostalgia.
That said, I only expect 1 or 2 additional 3rd party characters after Snake. However, I'd bet money that they'll come from these 4.
Nintendo Characters:
Little Mac (Punch-Out!!) - Factors contributing to his inclusion: Face of a Nintendo franchise, Nostalgia factor, a boxer would fit into Brawl extremely well, a boxing ring would work well as a brawl stage. Little Mac's could have his trademark star-uppercut as a special move.
Professor Hector (Gyromite) - Factors contributing to his inclusion: Face of a Nintendo franchise, Nostalgia factor, could include ROB as a special weapon/feature. Dynamite seems like an obvious weapon for him as well.
Captain Olimar (Pikmin) - Factors contributing to his inclusion: Face of a Nintendo franchise, could include creative gameplay mechanics with Pikmin.
Mii (Wii Sports) - Factors contributing to his inclusion: Promotion of Nintendo's Mii Channel, it would be reall cool to be able to play as yourself in Smash Brothers, cool weapons - bowling ball, boxing gloves, baseball bat, etc.
That said, I expect far more than 4 new characters. However, I highly expect these four. Professor Hector is the only I wouldn't be terribly surprised to see omitted.
Third Party Characters
Bonk - Factors contributing to his inclusion: He's the icon of a third party (Hudson), Nintendo has a great relationship with Hudson (see Virtual Console), Nostalgia. A Dinosaur land stage would work well.
Mega Man - Factors contributing to his inclusion: He's the icon of a third party (Capcom), Nintendo has a great relationship with Capcom (GBA Zelda titles, long history of 3rd Party support), Nostalgia.
Pac-Man - Factors contributing to his inclusion: He's the icon of a third party (Namco), Nintendo has a great relationship with Namco (Mario Kart GP, Star Fox Assault, etc.), Nostalgia. I do question what sorts of moves he would have.
Sonic - Factors contributing to his inclusion: He's the icon of a third party (Sega) and arguably the second biggest icon in video games (afte Mario), Nintendo has a great relationship with Sega (F-Zero GX, Mario & Sonic at the Olympics), long-time rivals, Nostalgia.
That said, I only expect 1 or 2 additional 3rd party characters after Snake. However, I'd bet money that they'll come from these 4.