Probably just a matter of time now.
I doubt even that is a sure thing...
http://www.nytimes.com/2011/09/04/sports/big-12-to-pac-12-oklahoma-ponders-a-move.html?_r=1
"Last year, the Big East engaged Kansas, Kansas State and Missouri in discussions when the Big 12 looked fragile. There is a good possibility that the Big East will follow a similar path toward expansion, especially considering the addition of Texas Christian to the league for next season."