There are no plans for a Vita version of Skullgirls. As far as I know all efforts are being focused on getting the XBL and PSN versions of the game out without hitch. I’d also suggest that you use the Questions & Answers thread.
Peter said that he is passing requests of Vita port to publisher or whoever they have as higher-ups so it’s possible. But they will not start it until consoles versions are complete. And I suppose that Steam release is higher on the list of priorities (although it wasn’t confirmed either).