In the end, and I have no evidence to back this, just a strong gut feeling, I think that Texas ends up in the SEC. The PAC schools are not going to bend over backwards to let Texas make the rules and in fact are more likely to only admit Texas if certain conditions restricting Texas are clearly spelled out. The PAC now is also not going to let Texas bring in a coalition with Baylor, TT, etc.
Texas doesn't want to separate from OU and OU won't go PAC without OSU even if the PAC offered OU which I think becomes less of an option. Texas is from an athletic standpoint in how they run the program a much better fit in the SEC and the SEC schools have big enough egos not to be bothered by Texas attitudes. For the SEC adding Texas (and a few friends) gives them the Texas and Oklahoma media markets and a lot of revenue potential. The SEC prominence gives Texas and OU shots at playing in the best football confernce in the country and getting paid well to do it.
If the superconferences form which I also think is eventually going to happen the PAC will snag some other schools from fast growing markets in the west that are more in tune with the PAC philosophy athletically and academically than UT/OU. Sacky is completely correct in where the the growth is. With the money coming in and population growing mid-majors right now could become major players in the future while still not threatening the balance that exist in the PAC. Schools like New Mexico, Boise, UNLV or Nevada have the potential to become quality fits, if the PAC wanted to expand its footprint even TCU might be a better fit than a beligerant Texas.
No question that Texas with the money it generates and the media market it dominates is a huge prize for any confernce that gets it but that prize is like marrying a supermodel, she looks great and brings a lot to the table but she wants her own credit card with no limit that the husband will pay for and everyone around better treat her like it is all about her. Outside of the SEC which already has schools with outsized egos and undeveloped morals any other conference getting Texas will be proud and happy at the outset but later on when the makeup comes off and the bitching and demanding starts the second thoughts will be constantly there.