To this point, no conference in the current BCS AQ structure has lost more than four teams in one year.
2003: VT, Miami, BC (Big East)
2010: Nebraska, Colorado (Big 12)
2011: Missouri, A&M (Big 12), TCU, WVU, Pitt, Syracuse (Big East...or MWC however you want to look at TCU's affiliation)
2012: Maryland (ACC), Rutgers (Big East)
It would appear, historically, that the death of these conferences is a slow process where you're picked to death.
If you look what's happened, recently, it looks like people swing for the fences early, get a good member, and then find an underwhelming #12.
2010: Pac-12 goes for most of the Big 12 South + Colorado. Strikes out. Gets Colorado and Utah
2011: SEC goes after Texas A&M and Virginia Tech. A&M says, "Yes." VT says, "No." SEC goes after Missouri. Tons of infighting, internal powers split, heavy money donors and fan support push them over the tipping point and they move. Otherwise, WVU would have been #14.
2012: Big Ten goes after Maryland and, probably, UVA. They get Maryland. Have to settle for Rutgers.
The trend is that if you need two, you get one that you want, and you get filler for #12.
Two teams voted against the buyout in the ACC. One is moving to the Big Ten, the other flirted heavily with us last year.
Take from that what you will. But I think assumptions that an ACC apocalypse is coming soon are premature.