Pretty much exactly what Texas has said all along
Texas No. 1 alternative is, and always will be, keeping the Big 12 together. It has and will continue to dominate the Big 12 because nobody except OU can even come close to competing with them for Texas recruits and there aren't any recruits relatively in the other Big 12 states. Its Nebraska and Missouri who are destabalizing the conference. Texas has about 35 times the recruits Nebraska has and that's not going to change.
Right now Texas and OU can count on a straight shot to a National Championship Game by beating the other. Count the number of times those two have been in the National Championship not including Texas near miss by decimal points in 2008. Why would they want to dilute that by dealing with USC which annually in this decade has had the best talent in the country