@Skidmark 's post above and the earlier post about how Texas isn't looking to be anywhere it can't dominate so is happy in the Big 12...
This is the key thing to remember.
It is why when I laid out a Pac-16 that could include Texas I framed it as I did.
Only way it happens is if the Big 12 breaks apart with schools like KU, OU and OSU leaving which results in a bunch of former G5 type schools and a further dilution of Tier 1 academic institutions.
With that, what the Pac-12 can offer that no one else could is a 4-team Texas Pod that UT would be able to politically dominate. Other concessions like the western semi-final game always being played in Texas (maybe somewhere "neutral" like the Alamo Dome), the Pac-12 purchasing the Longhorn Network and guaranteeing LHN money to UT, a rotation between San Francisco and Dallas for the Pac-12 Championship, hosting championships half the time in Texas for baseball and some Olympic sports... all those things and more could be on the table.
No other conference could offer that sort of package.
But it all depends on whether the Big 12 stays viable or starts coming apart.
Back to the political domination and why I said UH, TCU and TTU:
UH - beholden to UT if it gets into the Big 12, would be doubly indebted if UT pulled them along into a Pac-16
TTU - going back to the SWC had UT as an advocate and has always been like a vassal state to UT in voting, UT pulling them into Pac-16 only takes this to another level
TCU - has UT and DeLoss Dodds to thank for getting into the Big 12 and would also have UT to thank for getting into the Pac-16