Prinny is getting a sequel scheduled to be out in Japan in late March. Knowing the NIS translation cycle (also based off Prinny), we can probably expect this game state side some time between late June-late September.
-Game Play: The combo gauge now unlocks special attacks when full. Also a new easy difficulty called baby mode in which the prinny wears a diaper. Prinny Asagi is also playable.
-Bosses: An Alraune, female brawler (disgaea 3 look) with twin cleavers and a winged shark mount, male samurai, sorceress (disgaea 3), and a chick with a tank are confirmed. A screen shot of a large dragon near a check point might either be a boss similar to the one in Prinny or there might also be mid bosses.
-Enemies: Slimes (disgaea 3), thieves (female), and ghosts have been spotted. Orcs seem to now be mounted in tanks or parachutes. Gremlins can carry bombs.