It seems we're going to really change a lot like the Big East did. Pac and ACC are fooling themselves if they don't think they can be Big East 3.0 with a few key defections.
Here's as pertains to only Big East football in terms of the rapid instability.
2004:
Lose Miami and VTech
Add UConn as football program (was already non football)
2005:
Lose BC
2006:
Add Cincy, USF, Louisville
2012:
Lose WVU
2013:
Lose Syracuse, Pitt
2013: Dissolves as football conference
2014:
After one year in first year of American former Big East Louisville also joints ACC
After one year in first year of American former Big East Rutgers also joints Big Ten
UConn, USF and Cincy left holding the bag in American Athletic as the three short term Big East football programs that didn't end up in a traditional power conference, UConn eventually drops out of American to be an independent. In the end USF/Cincy just went up quickly and back to they were and the rest of the conference got absorbed mostly by ACC but 2 teams to B12/B10.
What will happen is the American will get a boost eventually from half of the new Big 12 joining with them if 3-6 Big 12 teams join Pac/B10/ACC, some of those teams will no doubt be American teams going back to American...or the Big 12 could keep Big 12 but with names like Kansas/KSU or OK State or IA State possibly gone it'll be nothing like the Big 12 or Big 8.
The only thing I really don't see is the SEC taking any of the New Big 12 or this new big 12 lasting for a decade plus as is.
There will be no reason for them to go back to the American. Regardless of how many schools get poached, it will become the home for the orphans and the best G5 programs. This is why the Big 12 is aggressively adding schools and why it was reported that they may expand again prior to the new TV deal. The strong G5 schools will have a mechanism to get rid of the weak teams and get themselves double what they would have had in the American. The Big 12 won't be what it was, but it will be a survivor.