Look at their options--they are limited.
If Big XII goes to 12, which of those 2 do you select? IF you think BYU is not top-2 on that list, based upon overall athletics, and what they bring in terms of fan base and markets, you do not get it. IT really would be up to BYU to do it or not.
And if rumors are true, which Clemson publically shot down, that Big XII was looking at Clemson and FSU, those 2 schools jump to the top of the list. But what if the Big XII wanted to go to 14? BYU is in for sure. I just do not see 16 happening. SEC stopped at 14, ACC has stopped at 14. 14 is too many. 16 is way too many.