By now they know exactly what BYU brings and what they are all about. If they don't like the offering and find others schools better, stop dinking around and make their move. BYU is not only the best candidate by far, it is also already the upper tier of current Big12 members in practically every metric that should be meaningful.
I'm to the point where I don't really even care that much either way. Big12 has given me enough reasons to be fine with life outside of that clown show.