Are Gearbox giving their time to the Vita? Who's actually porting the game? Because I'm willing to bet it's probably one of Sony's own teams, like Bluepoint, doing the work while Gearbox lie back and make some easy pocket change in the process. In which case, that'd be time and resources better spent on making something that can't be played anywhere else but the Vita.
Look, I realise there are people genuinely excited about the prospect of playing Borderlands 2 on the Vita and I appreciate that. I'm just airing my own personal grievances right now, and a port of a game from a series that I find is mediocrity incarnate doesn't get me hyped.