BSU only recently joined the MWC because they saw it as the best way to improve their chances of earning BCS bids. If a CUSA/Mountain West merger has a means of making that chance an AQ bid, what reason would they have to go to the Big East, particularly if it is an open question whether or not the new Big East will be AQ?
Sounds like the CUSA/MWC conference will likely operate like two leagues, except in football which will hold a championship game, hopefully for the AQ bid. If true, there would be little change for most teams most of the time.