If Texas and A&M leave the Big 12, along with Nebraska, CU, and Mizzo, the Big 12 will aggressively pursue TCU. Of course, if that all happens, OU will be out the door as well, so I don't think the Big 12 will be worth joining. Without Nebraska, OU, Texas, and A&M, the AQ status will be long gone, as will the TV money. No reasonable TV exec is going to want to lay out money for Texas Tech vs. Iowa St.
And if the Pac-10 and SEC are in Texas, the Big 12 will be lucky to get any coverage in DFW, Houston, Austin, or San Antonio.
Ranking value of the schools in Texas in terms of TV value, I make it
1. Texas
2. Texas A&M
3. TCU
4. Tech/Houston/SMU
5. Baylor/North Texas/Rice/UTEP