We currently allow no gay professors or students at the university unless they promise to remain celibate--even if they are married. This position is considered discriminatory by nearly every public university and by most courts that have considered it. Even Notre Dame employs openly gay professors and admits gay students. I can think of only Baylor as a P5 university that may have a similar policy.
Public perception will continue to evolve and BYU's policies will be seen more and more as discriminatory. It's is inconceivable to me that the PAC 12 would be willing to affiliate with BYU when "diversity among students athletes, coaches and administrators" is one of the stated values in its official bylaws. I think its possible that the Big 12 may take us, but I think that window will close before too long.