Honestly, I could see the SEC going to about 32-45 teams.* The NCAA completely failing (at least in Division I), and three or four mega-conferences taking over their own governance.
The SEC will thrive. The B10 will survive, and probably the PAC, too. Those two might group up into one, if they can figure out how to get all the egos out of the way.
The B12 and ACC are likely dead, if this plays out to that extent. Over half the ACC will come to the Mega-SEC (whatever it comes to be called), and the B10 will take what's left. The SEC and PAC will split some of what's in the B12, but a few of those schools might have to drop to Division II or eke out a miserable existence as independents.
I honestly can't see how independents survive, though, if this does play out. Being in some organizing body will be necessary, just to get enough games to make up a season. Cross-conference play will cease to exist. At least for a while.
Group of 5 conferences will see a similar merger. Every one of them will be poached by the Power conferences, but what's left can group up and make a decent new litttle-brother-mega.
The fun thing will be seeing what happens in the years AFTER that realignment. Will, one day, the winner of the Mega-SEC and the winner of the Mega-B10-PAC meet in a new "championship bowl"?
Whatever happens, we are certainly suffering the Chinese curse of living in interesting times.
* Current SEC 14 plus 10 or 11 from the ACC (Clemson, UNC, NC State, Duke, Wake, Miami, FSU, Va Tech, Ga Tech, Louisville, and maybe Virginia though they could go to the B10 instead), 4 to 6 from the B12 (Oklahoma, Okla State, Texas, Texas Tech, and maybe TCU and/or Baylor), one from the B10 (Nebraska), and anywhere from 5-15 from G5 conferences (UCF, USF, Memphis, Houston, Western Kentucky, App State, MTSU, Charlotte, UAB, La Tech, Southern Miss, Coastal Carolina, Ga State, UL Monroe, Arky State, etc.)