I'm not convinced. It really depends on a lot of things. Does the Big Ten go to 16 and if so, who do they go after? I think its most likely they are the first to jump to 16. I also think they are far more likely to take Kansas/Oklahoma in order to shore up their basketball roster in competition with the ACC, who has become the premier basketball league after its raid on the Big East. UNLESS, that is, the Big Ten can grab North Carolina. In fact, I think UNC is the prime target in the next expansion wave, along with Virginia. I think the SEC and Big Ten both covet both schools. It's two states neither conference has a footprint in, with large (and growing) population bases.
If the Big Ten expands, and I think they will, then the SEC will follow suit. It could come down to a bidding war of sorts for UNC/Virginia between the Big Ten and SEC. Both conferences offer unique things to each school. The Big Ten? Mythical academic superiority. The SEC? Cultural and regional fit, which I think go a long way but probably not as far as the academic superiority goes with the pinheads that run the universities and ultimately make these decisions. So then, does UNC/Virginia even want to leave the ACC? For the money probably so. It would be a substantial pay raise.
At that point, if the Big Ten outbids the SEC for UNC/Virginia, the SEC must decide if it wants to try to pick up the second team in North Carolina and Virginia (Duke, NC State, Virginia Tech) or if it wants to look west. This is where Oklahoma to the SEC might have a chance. However, I believe the SEC would much prefer expanding into North Carolina and Virginia, even if it meant getting a second tier school. So do those second tier schools take up the SEC's offer? For the money, I think it's a no brainer that they do. If they turn down the SEC, then I think that's when they settle and go west. But they will prefer only Oklahoma, not Ok State, and I think they try to get Kansas to come along for the basketball upgrade.
So the Big 12 dies. Texas is forced to go to the Pac 12 along with some combination of what's left, in order to get the PAC to the PAC 16.
The ACC loses either 2 teams or 4. They will get back up to 16 by adding West Virginia, Cincinnati, and/or UConn and Memphis.
Notre Dame is a massive wildcard, obviously, but would likely maintain it's relationship with the ACC if possible.