After reading recent comments from the power 5 commissioners about the future of the FBS, it appears that there will either be a new FBS subdivision or the power 5 conferences will leave the NCAA and form their own college athletics association. With the enormous popularity and financial success of the NCAA men's basketball tournament, I can't see either the NCAA or the power 5 football conferences parting ways.
Many "experts" are saying the power 5 conferences along with Notre Dame, BYU, and a few others will form a new 65 to 80 FBS division. I believe that a new FBS division will be formed but believe in the end that it will be closer to 90 than 65. I think politics will play a huge role in the final make-up of the FBS I (that's what I'm calling the new division).
In 2014, the FBS will have 129 members and the FCS will have 126. Politics will get the AAC and MWC into the FBS I along with half the CUSA schools (Rice, Southern Miss, UAB, Marshall, UTEP, and LA Tech). Since Navy and Air Force are in, Army will be too. That gives the new FBS I 97 members. That means 32 current FBS schools will be left out. That's bad news for the MAC, Sun Belt, and remaining CUSA schools like ODU and Charlotte.
The FBS 2 with the MAC, Sun Belt, and CUSA will likely add a few FCS conference like the Big Sky, CAA, and/or SoCon to get to 60 to 70 members. If the entire conferences don't move up, I still think there will be as many as 30 FCS schools joing FBS 2. I can see schools like Liberty, JMU, Furman, Delaware, Villanova, Eastern Washington, Montana,... moving up. The FCS will drop from 126 member schools to 90-100 schools.
This movement of subdivisions has been occurring for the past decade. That's why you're seeing schools jump from CUSA to the Big East (now the AAC). That's why the WAC football conference recently died and most of their football members are now in the Mountain West. It looks like this game of NCAA Division I musical chairs is far from over.