As you said, the PAC is the weakest P5 conference (Please Yewt fans, don't bore us about the "conference of champions"...no one cares). In the "modern era" of CFB, only two PAC teams have won a national championship (USC, Washington). Colorado's 1990 championship was from another conference. NO PAC team not named USC has won a national championship since 1991.
The PAC's media deal sucks...for a P5. It still can't get its networks on DirecTV. It's games start at crazy times in the midwest and east coast. No one east of Colorado cares...at all.
At this point, if there is to be realignment, It's much more likely that the BIG12 picks off a PAC team as opposed to a BIG12 team leaving for the PAC. No one cares about Cal, Oregon State, Washington State (this year's success aside), Utah, Arizona or Colorado. There are only six PAC programs worth anything: Washington, Oregon, Stanford, USC, UCLA (maybe), and Arizona State (maybe).
Football drives this bus. The PAC is in for a long, slow, steady decline without MAJOR change...Major change could just kill the PAC.