Nippon Ichi's summer greeting card appears to hint at Disgaea 5

[Kresnik]

BraLoD said:

Probably PS3, then Vita latter. (as it always get a portable version as well, but different from the main console game).

I think it's likely to be a PS4 release.  They've been hinting that they've been working on a PS4 title for a while and the timing is too good for it to be anything else, imo.