In the end, when the final rankings come out, the Committee will just do what they want. TCU dropped 3 spots in the final poll in spite of having a more impressive win the final week than 2 of the teams that jumped them.
There's no reason that the Committee couldn't/wouldn't just do the same thing to BYU: we need to rank them at #X so we can justify not including them...done! It doesn't matter what BYU had been ranked previously. BYU, its fans, Kirk Herbstreit can cry about it all we/they want, but the final rankings are the final rankings.
Add and win 1/2 more games and leave no doubt!