I just don't see the SEC or the Big Ten losing any schools that they currently have. I doubt the PAC 12 loses any either, but I don't see that any other league would be interested in those schools anyway due to the extreme geography.

Allow me to posit this:

Movement doesn't start in earnest until the GORs expire in about 10 years.

The SEC, having already expanded into the Midwest, decides to become a broader national force. The TV money, the recruiting, and the overall exposure are too tempting to pass up. In order to accomplish this, you need national brands of which several are now available after the end of the GORs.

Texas, Baylor, Oklahoma, Oklahoma State, Kansas, Iowa State, and BYU are recruited to form a new Western division.

In the East, the ACC is finally dealt its death blow. UNC, Duke, Virginia, Florida State, Clemson, Georgia Tech are brought into the fold.

Notre Dame is offered a spot as well. Highly possible they decline, but for the purpose of this exercise let's say they accept in order to avoid losing exposure in growth markets.. In the wake of that, the SEC moves North again with Syracuse, UConn, Boston College, and Pittsburgh.

That's 32 strong brands from various regions of the country. The SEC is in a unique position to bring them together if they were to choose to do so.

West: BYU, Kansas, Iowa State, Missouri, Oklahoma, Oklahoma State, Texas, Baylor
Central: Texas A&M, Arkansas, LSU, Ole Miss, Mississippi State, Alabama, Auburn, Vanderbilt
East: Florida, Florida State, Georgia, Georgia Tech, South Carolina, Clemson, Tennessee, Kentucky
North: Syracuse, UConn, Boston College, Pittsburgh, Virginia, North Carolina, Duke, Notre Dame

7 division games, 2 permanent rivals from any of the other divisions, 2 more games on rotation with the rest of the league with conference semi-finals to follow. I know that's a massive league, but it removes the need to play OOC games as virtually anyone you would be interested in playing is in the league. Every game's value is increased by the fact that it's an intra-conference game rather than simply an inter-regional game.

The B1G takes Virginia Tech and NC State to fill out their roster. It's possible then that they move to combine with the PAC 12 to counteract the SEC's power grab.