If we do go to 12 teams, I would look for Oklahoma and Texas to be in separate divisions possibly. 4 Texas schools plus 2 Oklahoma schools in one division won't fly IMO.
I personally don't see it happening - Oklahoma and Texas being split, that is. If Oklahoma and Texas were to be split neither school would want to give up the Red River Shootout - that's a big moneymaker for both schools. That would mean they would have to be each others' protected rivals. At the same time, neither school is going to want to have to go up against each other twice nearly annually just for the right to play in the conference championship game. Plus having Texas v. Oklahoma in the Big 12 Championship game nearly every single year is just setting yourself up for yet another round of conference instability.