If you have the Big12 reduced to 6 or 7 teams, then I could see them, perhaps, inviting any number of the pool of MWC +BYU, as the final couple after they first poach the AAC. I have a hard time seeing the Big 12 looking west for expansion. I think the PAC12 is pretty confident in its position out west. Frankly, most eyes are east of the I-35 corridor and it'll be a hard sell for late-night kick offs which are used as late night inventory fodder. If, and only if machinations and rumors indicated a western expansion then I could see the PAC12 perhaps make a move, but I doubt it.
I think half the AAC should be sweating right now. I'd venture the MWC and PAC 12 are darn near irrelevant in this whole thing.