A sequel to the original Disgaea is in the works. Coming out in Q1 2013 in Japan is Disgaea D2.
Rather than continue on with a new main character and a higher number, the newly announced Disgaea D2 will be a direct sequel to the original Disgaea: Hour of Darkness. Laharl, Etna, and Flonne will make their return as the main characters for the new game, and it will tell the story of what happens with them after the first game.
Disgaea D2 will be released exclusively for the PS3 on March 20, 2013 in Japan.