I think there is a bylaw for the BCS that was discussed last year when the Big XII was about to blow up that requires a conference with an autobid to retain at least 5 of its member schools in order to keep that autobid. It was talked about because the Pac-10 was going to take 4 from the Big 12, and then the raiding would begin to get to 16, and the Big XII would be left with 4 schools (something like KU, KSU, ISU, and CO? I've heard too many rumors to keep track anymore). With 4 members, even if they in turn absorbed the MWC schools, they wouldn't get to keep their autobid.
The relevance is that if the Big XII does indeed take Louisville and WVU, and does so for the 2012 season, they will be down to 4 members, and lose their autobid - and then chaos will ensue with the resulting power vacuum.