I think it will probably happen if the Big East Presidents can come around on it. The Big East needs some football legitimacy right now and Boise State is as good as they're going to get.
Keep in mind that such an invitation would be football-only in nature, so it's not like the Boise State volleyball team will be forced to play at Seton Hall on weeknight nights or something. I agree that THAT would be crazy, but if Boise State comes in as a football-only member, then it's not that out-there, really.
For Boise State, it would mean more money and it would also mean that they wouldn't have to go undefeated to get a BCS bid. And, to be honest, the only team in the Big East right now that has much of a chance at beating the Broncos is WVU, so Boise State probably would go to the BCS quite a bit.
And if WVU goes to the Big 12 or SEC, then Boise State should cruise to the Title...