Who do you think, and why. And of course, there's the obligatory "other - please specify" option.
From what I've seen so far, I think it's going to be Rogue. Honestly, that just comes out of a process-of-elimination. I can't see them getting rid of anyone else, unless it's Angel - but he hasn't had much screentime, and he's "out of the picture" currently, so I wouldn't care much about him buying it.
(Other options that would not fit in the pole include, but are not limited to: Emma, Canonball, Sunspot, Polaris, Havok, Angel, Xavier, Cable, Psylocke, Magician, etc.)