realized that without USC/UCLA/Washington/Oregon the PAC-12 wasn't going to be a viable option financially - even if they DID backfill with MWC schools.
A PAC-12 where USC/UCLA/Washington/Oregon were replaced by Boise St./Fresno St./Colorado St./San Diego St. was basically rejected when those schools decided to bail to join the Big 12. I would be surprised if they were to change their minds now and go back.
Their only real shot at luring P4 schools away, IMO, is if the ACC experiment ends up not working for Stanford and Cal due to travel costs and/or the ACC falling apart if and when Florida St., etc. jump to the SEC.