They didn't extend the grant of rights because they don't have to extend it and there is no really good reason for doing so.

The only reason for Texas and OU to agree to an extension of a grant of rights is for purposes of negotiating the Big 12's next television deal. That deal is not yet up for renegotiation. I suppose they might also extend the GOR if they thought it would help attract new conference members. But the BYUs and UCFs of the world will join the Big 12 in a flash, no questions asked, without the need for a longer GOR. Assuming there was some big fish out there (hypothetically, let's say Florida State) willing to move from a P-5 conference to the Big 12, extending the GOR for Texas and OU might be part of the play. But a move like that - which most people on this board think is unlikely anyway - isn't going to happen until the GORs and television deals of other conferences near expiration, which again will be several years down the road.

It really makes no sense for a Texas or Ohio State or Alabama to sign or extend its grant of rights beyond the length of the existing television contract of their respective conferences (if at all), at least until the end of that deal starts to approach. Those schools are going to be fine under any and all circumstances that may come to pass, so signing away rights is just giving up leverage that can be used for a multitude of purposes.

A GOR really does nothing more than set a time frame for a conference member's next decision point in conference life. Everyone is going to make those decisions. Depending on the conference, that decision is going to be made a few years from now or more than a decade from now. But having a time frame for making that decision does not necessarily dictate the decision itself.

Would I be surprised to find Texas and Oklahoma in a different conference ten years from now? Not at all. But I also would not be surprised to see them remain in the Big 12, because as long as the money is right it is arguably better to sit in a position of power than become the vassal of the long-standing heavyweights of some other league.