The concept of regional conferences in Division 1 is extinct. Conference membership and alignment is more about media markets and the number of eyeballs (sports consumer dollars) the teams in the conference can bring to the viewership table.
Oklahoma and Texas are moving to the SEC because they have a better TV deal than the Big 12. USC and UCLA are moving to the B1G for the same reasons. If the ACC can't improve their media deals you can expect Florida State and Clemson, at least, to move. With the PAC whatever number they end up being network on life support, you will see schools like Oregon, Washington, Arizona/Arizona State, and Utah moving if they are given the opportunity unless the conference gets their act together.
It's a brave (not so new) world that you can trace back to the mid 1980's or so when college football broadcast rights were being negotiated between the networks and ESPN.