Nippon Ichi has announced Disgaea 4 for Japan and state-side, and seems to be betting the farm on it. In fact, N1 seems a little desperate. Rumor has it there's a collector's edition in Japan for over US$100 and all it includes is the OST and a figurine of this gal:
Yeah, there seems to be a pretty big emphasis on prinnies this time around.
If that doesn't seem like $40 worth of Collector's-ness, it's probably because the standard edition is priced around $80, or so I've heard, so it's really only $20. I don't imagine they'll use those prices state-side as in America, that dog don't hunt.
The sprite art has received a huge update, which is great since they looked awful in Disgaea 3.
The protagonist seems to be some sort of vampire, which means little to me other than a few guaranteed Twilight jokes. Hopefully the story will be better than in Disgaea 3, which crumbled under the weight of the weak and illogical joke that comprised its entire setting.
I'm also hoping there'll be some sort of benefit to having played Disgaea 3 and purchased the DLC. All $50 of it. Given N1's dire financial straits, I'm guessing two or three extra characters for playing D3 and nothing for the DLC.