This, I assume, is what has continued the rumors of an expansion to 14 with the two Arizona schools, Colorado and BYU.
My own speculation now: I think the best option for BYU in 2024 would be that either Nebraska or Colorado wants to come back to the Big 12. Then the Big 12 would likely extend an invite to BYU to join as a partner. Both wanting to come back would close the door. The AZ schools wanting to jump would close the door.