I suspect the more likely scenario is that the Big Ten & Pac 12 move their higher ranked teams elsewhere (most likely a game in LA). Remember that the Holiday Bowl already lost its higher ranked tie-ins a few years ago to more money in other bowls.
Then the San Diego Bowl Committee decides to take the Las Vegas Bowl's current matchup away from them for the Holiday Bowl (or maybe even push to get the Pac 12 #4).
Finally, I suspect they will let the Poinsettia Bowl go away.
While ending the Poinsettia would suck for the MWC, the champion's matchup would finally get a proper date after Christmas coming full circle back to the old days of the Holiday Bowl.