There are a few developments coming out of the Big East which look to have a negative affect to the Mountain West's stability as a league. The first which came out earlier today which was that the Big East is considering not adding schools from within a state where they currently have members:
What is happening is the league, or the conference, now is looking at schools and they have looked very much at schools that are not in any of the states that are represented by the Big East schools right now. The ones that they're looking at right now, they do not sit in any state that the Big East schools currently are in.
That means no Central Florida, Temple, Army and possibly Houston, depending on what they think of expanding eastward. This is good news for Air Force since they are obviously not in any of the states where a current Big East school resides, so the odds of them becoming the latest member is increasing.
Now there is this tweet from Jon Wilner of The San Jose Mercury News: San Jose Mercury News' Jon Wilner
That does not say that Air Force has not accepted an invite to join the Big East, but it will be hard for them to turn one down.