Disgaea 3 (Japanese version) should be out for the PS3 soon and based on current trends, the US should expect the game in late summer to early fall (we usually get these games about 7-8 months after the Japanese release).
http://www.youtube.com/watch?v=217q6a81MXEFrom what I've seen in the opening scene, Laharl, Etna, Flonne, Axel, the main heroine from Phantom Brave?, and all seven Prism Rangers make cameos. As for playable classes we get archers, gunner (male), heavy knight, male and female warriors, beastmasters, ninja (male), ninja (female), geomancers, samurai (female), gunner (female), either a unique bow user or a male archer, mage (female), rogue (female), prinnys, wood golems, several monsters from Makai Kingdom (the cats, mushrooms, and skull things), succubi, ghosts, and flower things (from D2).
The main characters of this game are Mao (nerdy guy with glasses) and Rasberyl (the girl with pink hair, probably gets changed to Rasberry in the US version if it comes).