We should just shut down BYU's athletic program if it becomes so bad in the near future that the MWC wouldn't immediately offer us terms at least as good as BSU's arrangement (which really isn't all that great, since the MWC retains all of BSU's home TV revenue, and both the MWC and BSU have to agree on any broadcaster for BSU home games).
BSU and BYU are to the MWC like OU and UT are to the B12. OU/BSU arguably is the better team, but UT/BYU is the league's biggest fanbase/market. If BYU football ever sinks so low that the MWC wouldn't treat us the same as BSU, then it would be time to cancel BYU football and all the other sports it funds.
We also need to remember that BYU's primary reason for going independent was control of home TV rights. Yes, being independent makes it easier to jump into a P5 league, but that's only a secondary benefit. Thus if the B12 expands east, then BYU's primary indy benefit hasn't diminished. It's still intact and will be until 2018 and likely beyond, and BYU will avoid changing that until 2019, at the earliest.
HOWEVER, if all P5 teams ever collectively refuse to play BYU (leaving BYU with a G5-only schedule), then it might be time to shut down the athletic department, but that likely won't ever happen since teams from the SEC and other P5 leagues like to "schedule down" for at least one or two of their non-conference games.