Contrary to the TCU fans, CUSA is probably the most stable non-BCS conference. They could lose some schools to the BE, but the 6 western schools aren't going anywhere. They are satisfied to be together and, noone else really wants them. Nobody wants UAB and USM going to the BE is pretty far-fetched. So there are 8 members who aren't going anywhere. WAC and MWC are vulnerable to Pac 10/Big 10/Big 12 expansion impacting them and to each other as each only have 9 members. MAC and Sun Belt are vulnerable to the 15k attendance rule.
I understand where SDSU, UNM, and UNLV would like to be playing in a league with Fresno, Nevada, Boise, Hawaii.
Compare the less desirable half of the league though. Would SDSU, UNM, and UNLV rather play Idaho, UtahSt, NewMexicoSt, and SJSU then Wyoming, Colorado St, Air Force, and TCU. The answer is no. SDSU, UNM, UNLV would rather stay in the MWC and add Fresno, Nevada ect, then join them in the WAC. And why would SDSU, UNM, UNLV want to pony up entrance and exit fees to rejoin the WAC?
Which line up would have more TV value?
NewWAC-SDSU, Fresno, SJSU, Nevada, UNLV, BoiseSt, Idaho, UNM, NMSU, USU, Hawaii
NewMWC-SDSU, Fresno, UNLV, Nevada, BoiseSt, UNM, ColoradoSt, Air Force, Wyoming, TCU, Hawaii
This WAC raid of the MWC is almost as stupid as the idea of the WAC raiding CUSA for Tulane and Houston before SMU, Rice, Tulsa, and UTEP moved to CUSA. The WAC is where you play when you can't get into the MWC or CUSA.
And the raid of the MWC by the PAC-10 is much more theoretical than the raid of CUSA by the Big East. And the PAC-10 would at most take 2 schools from the MWC. The Big East could take four from CUSA.