Remember, the PAC12 is adding SDSU, SMU, and reportedly also Colorado State and 1 other (Rice or Tulane)
And there is the risk of Oregon and Washington leaving at any moment to the BIG TEN.
Who in the BIG12 wants to join that? Maybe TCU would be the most likely option, but even then, they have a great set up in the BIG12 with other Texas schools (Baylor, Texas Tech, Houston), and regional schools. I also doubt that Kansas would be interested. They are doing fine the BIG12.
The PAC12, not the BIG12, has the major problems to worry about.