I remember reading last year that to keep AQ status a conference must have 6 members that have played each other for at least 5 years according to the NCAA.
That doesn't look good for the remaining teams in the conference. I think Mizzou is the next to leave anyway, so the Big XII will be down to 4 if that happens. When UConn and Rutgers go to the ACC, and WVU goes to the SEC there will only be 3 football teams left in the Big East.
NEITHER conference will be able to keep AQ status.
That is for NCAA tournament not BCS. BCS is not governed by NCAA. I outlined it earlier on here. AQ status is base on contracts with the BCS bowls. Both the Big East and Big 12 have contracts so whichever conference remains keeps it.
In 2014, it will be reevaluated. The current rules state that you have to be in top 6 in 2 of 3 categories as outlined on BCS website. It might be changed then, but each conference plus ND have a vote (total of 11 if merger happens). 4 super conferences plus ND would not be enough for a majority to change any rules, so the new conf would have a lot of say in the rules for remaining an AQ conference.
I have actually researched this instead of just "guessed" and then made a conclusion based on that.