I don't like being the bearer of bad news (and I really hope by some freak chance I'm wrong), but according to Omar, the person directing the game, the 20 characters revealed so far are all we're getting on the disc:

Part 1 of the Playstation All Stars Battle Royale EB Expo Interview

Notable FAQ Quotes About the roster

So this is confirmed to be the final roster on the disc:

Big Daddy
Cole MacGrath
Colonel Radec
Dante
Evil Cole MacGrath
Fat Princess
Heihachi Mishima
Jak and Daxter
Kratos
Nariko
Nathan Drake
Parappa
Raiden
Ratchet and Clank
Sackboy
Sir Daniel Fortesque
Sly Cooper
Spike
Sweet Toot
Toro Inoue

Yeah, no Crash or Spyro, which were probably the two most requested characters for this game.

Personally, I'm still wanting to play it, but not nearly as much as before.