At bottom, I think you are right; any litigation of the issue would likely lead to a negotiated resolution, which means dollars.

I do think injunctive relief is a possible, albeit short-term remedy. It is short-term because the relief would be limited only to the contractual period during which the GoR is effective. It is possible, however slight, because injunctive relief is predicated on irreparable harm. Hypothetically, if Texas and Oklahoma broke up the Big 12 I can surely see schools like Iowa State and Kansas State and West Virginia and Texas Tech and Baylor arguing that their athletic programs would suffer irreparable harm by the dissolution of a P5 conference in which they are members.

The reality is that litigation of the issue is unlikely. When you compare the length of the GoR with the burden and expense and loss of good will that would result from litigation, the scales weigh heavily in favor of the status quo. Litigation of these issues is only going to get hotter and nastier. The lawyers who get hired to handle these things are absurdly expensive. Every then-Big East school that sued the ACC when Tech and Miami defected lost money on the litigation. If Maryland does better than break even, it is only because the rest of the Big Ten supported the Terps against the ACC and the ACC was not shrewd enough to sue the Big Ten schools individually.

Apart from Texas and OU, there are no schools in the Big 12 that are worth fighting over from the perspective of other conferences. And Texas and OU have it too good now to bother with the costs of litigation. So as much as OU wants to stomp its feet, Texas knows OU is almost certainly not going anywhere until the GoR expires.