The Longhorns would be stupid to join the Big 10. It’s not a fit geographically or any other way. Even the Big 12 is not a great fit but it’s infineitly better than the Big 10.
Besides, top to bottom, the Big 12 is stronger than the Big 10.
Also, the Texas Legislature has made it clear that Texas and Texas A&M are both going to have to remain in the same Conference and A&M is not going anywhere. They wanted to join the SEC when the old SWC folded but UT wanted to form the Big 12 so they reluctantly went along.
Unfortuneatly, they haven’t been worth a damn since.
I believe the Big 12’s TV contract will be coming up for renewal soon. That is a good incentive for its members to stay- especially since the Big 12 ought to land a huge deal with ABC/ESPN.