Disgaea 2 Portable is confirmed to be the real deal. The port of the PS2 game will be released in Japan on March 26.
The port will be getting 30% more content, with new scenarios and characters. There are unannounced features as well, but these weren't revealed, though the magichange system of Disgaea 3 is more than likely (see screenshot above).
No news on a release date for other regions yet, but we'll be sure to keep you posted.