I agree that Florida State and Clemson will wind up in the SEC, but I think it may take a little longer than you estimate. I believe the SEC will need Texas and Oklahoma to join officially before taking a vote on Florida State and Clemson, otherwise the Gentlemen's Agreement could defeat it.
Once that happens, I think the floodgates open. I see the B1G grabbing Virginia, North Carolina, Georgia Tech and Miami (for a presence in Florida), and the SEC also picking up NC State and VaTech (for a presence in those states).
That leaves six teams in the ACC. BC, Pitt, Syracuse and Louisville will stay together based on common past in ACC and Big East (although BC and Louisville were never in the Big East at the same time). Duke and Wake will stay with them because, essentially, they have no other option remaining. From there, full merger with the Big XII is a possibility, but I think the more likely scenario is that they take the three easternmost teams in the Big XII (UCF, Cincinnati, WVU). In that event, merger with the Big East is also a possibility, but I think the more likely scenario is that they offer 3-5 from among UConn, East Carolina, UMass, Memphis, South Florida and Temple. So the ACC stays together in some fashion, but possibly under a different name and certainly severely weakened.
Big XII suffers a similar fate. Pac-12 may as well, especially if SEC and/or Big 10 embraces the concept of football-only membership for those schools. Again, here the conference figures to be severely weakened but probably survives in some form. Beyond USC, there's a considerable dropoff in demand for these schools.