If Oklahoma beats Texas Tech and Oklahoma State (which I think they will) they will go to the Big XII Title Game. I would fully expect them to beat Mizzou, and in doing so head to the National Championship to face the winner of the SEC Championship.
It appears that Texas is screwed either way. On one hand if OU wins out, they will get leapfrogged, and if TT wins out obviously they will stay ahead of them. It doesn't look very likely that Texas makes it to the Big XII Championship much less the National Championship. It's also too bad there can't be more than 2 teams from the same conference in the BCS because Texas Tech, Texas, and Oklahoma in reality should all be there.