At Akihabara Electric Town Festival 2011, Nippon Ichi Software (Disgaea, Phantom Brave) gave a couple hints about future plans.
First of all, they're making sure the 3DS port of Pixel's indie Metroidvania action-platformer, Cave Story, comes to Japan. No news on the release date, but it came out in North America last month.
Then, a hint about a new adventure game: "It's not [another] Hayarigami [game], but it will satisfy Hayarigami fans." So maybe we can assume it's in the horror genre as well?
Finally, some info about another new game, this time a dungeon crawler. The team behind Disgaea is developing it, and there are three key phrases:
1. Seven angels
2. High res characters
3. Superior Custom[ization?]
We'll definitely be keeping an ear to the ground for more on these new titles, including...their titles (!) which remain unannounced.