I wish I'd kept the quote, but back about 2005 an associate athletic director at Duke, when asked about the forming of superconferences and the potential for them to break away from the NCAA to form their own association, said that the NCAA is a voluntary organization*, meaning schools don't have to be a member and could leave at any time to do their own thing. The notion of the "above the line" or "top 5" BCS conferences going their own way is not that outlandish.
But remember, money, not what is best for college athletics, will drive all the decisions. You can bank on that. Always has; Always will.
*UND fans are brutally aware of that for the last few years.