My guess is that Texas and Texas A&M and the SEC are crossing t"s and dotting i's on the contract right now. Not enough has been said or written about schools to the East for me to have a good take on that, but I am sure the SEC would love to have North Carolina and Virginia Tech.
I do not see UNC leaving unless Duke comes along. The basketball rivalry is just too deep and important. And while they could play as non-conference foes, it would lose too much in my opinion.
Too deep to get into now, but I was privy to a plan being formulated by Jeremy Foley around two years back that involved Florida, Georgia, Syracuse, and
either Alabama or Tennessee moving to the ACC to form a North-South superconference. The thing was pretty impressive on all three of the men's fronts (football, basketball, and baseball). And the major TV markets from New York to Washington, to Charlotte, to Atlanta, to Tampa, to Miami - and Birmingham, were tied into the deal. The money was outstanding. The UF President nixed the idea. Have to see what he thinks of the plan now.
But think about a football league with Miami, Florida, FSU, Alabama, Georgia, Georgia Tech, Clemson, and Duke on one side and Boston College, Syracuse, Maryland, Virginia, Virginia Tech, North Carolina, North Carolina State, and Wake Forest on the other. I think it is too heavy on the South side of things, but good grief. And the basketball would not be bad either.
But back to the current thoughts.
At least one of the new schools would have to be a major Texas school - and I do not see TCU, Texas Tech, Baylor, or Houston bringing enough TV ratings to justify their inclusion. And since UTx and aTm will not move unless as a pair, they have to be included. Personally, I would stop with those two and stick at 14 members.
Remember, each new member needs to bring at least a $17MM per year increase in rights fees to justify their invitation. FSU, Georgia Tech, Clemson, and any of the North Carolina schools not named Duke or UNC will not meet that target (the latter two will on basketball alone). Miami is iffy (UF is not the total dominate TV program below Orlando). Virginia Tech might because they would open up the Tidewater and possibly Richmond/DC markets (the former much less certain). Louisville I would have to research more to formulate an opinion.
If 16 is the magic number. I would go with UTx and aTm in the West. And two of UNC, Duke, VA Tech, and Miami in the East. My preference in the East would be UNC and Miami, but I imagine UNC and Duke would not go unless as a couple (much like the two Texas schools).
So, a West of Texas, aTm, Arkansas, LSU, Miss, Miss State, Alabama, and Auburn. An East of Vanderbilt, Tennessee, Georgia, Kentucky, Florida, South Carolina, UNC, and Duke. A little too strong on the West for football (maybe switch Vandy and Auburn) and WAY too strong on the East in basketball (which matters less in the championship hunt) - (so maybe switch Kentucky and Auburn instead).
Every TV market from the Texas border with New Mexico to probably DC (Duke and UNC are strong up there) would be SEC Turf.