I live in Texas. I have yet to talk to somebody down here that doesn't think BYU should be added if the the Big 12 expands.
Note, none of thewe people are LDS, and include Kansas, Kansas St, Texas, Iowa St, and Oklahoma St fans. It also includes fans from several Big 10 and SEC schools. So in general I feel if expansion happens BYU has to be in. I'm just still not convinced the Big 12 will in fact expand right now.