It appears that Air Force's move to the Big East is gaining steam. Following Sunday's news that the Academy is actively seeking Big East membership, the conference's school officials have authorized commissioner John Marinatto to pursue additional schools for expansion. One possibility mentioned in the previous link is that the Big East will invite the three service academies (Army, Air Force and Navy) to join the conference as football-only members, which makes sense since those teams are members of other conferences in other sports. Air Force is likely to move its other sports to a conference like Missouri Valley.
According to Kelly Whiteside of USA Today, the Big East will make its expansion moves "quickly" and will definitely want to add Air Force and Navy. Army is also a possibility, she suggests, but we'll need to wait on all three.
TCU is expected to accept an invitation to the Big 12 conference before even stepping foot into the Big East, which they had agreed to join last year.
For more on the Mountain West and possible realignment, visit Mountain West Connection.