It seems Disgaea 5 isn't the only game Nippon Ichi Software have in store for Playstation 4.
In an interview with 4Gamer.net, company president Sohei Shinkawa stated that another title is being prepared, and the risks involved with seizing the initiative & moving to the next gen systems:
“We’re already preparing [another title] for PlayStation 4,” Shinkawa said. “So, to fans of Nippon Ichi Software, if you buy a PlayStation 4 to play Disgaea 5, rest assured that we’re preparing other titles coming afterward.”
“If, for example, we’re off our release schedule by even a week, that’s enough to affect our performance for this quarter,” Shinkawa said. “But when you look at it in the long term, it’s really important for a small company like ours to take that initiative of putting out PS4 games with this sort of timing that we’ve got going, so when it comes to console projects moving forward, we’re looking to transition into development for the PS4.”Source [4Gamer] [Gematsu]