The contract for the BYU series contains Language that could allow BYU to break the Starkville trip if they join the Big 12 in 2017.
Before we begin, let me reiterate that NOTHING IS OFFICAL. So there is no need to panic yet. But the possibility of this game happening in 2017 does have some question marks.
Vanquish the Foe wrote an article in 2015 about the contract details of the Mississippi State BYU series. In it there is language that would protect Mississippi State if the SEC were to go to nine conference games OR protect BYU if they were to join a Power 5 conference like the Big 12.