The Big East is really in a tough spot. There just aren't any logical programs that they can add to their conference to improve football. They are surrounded by much more stable conferences where they aren't going to steal any teams from the ACC or the Big Ten. Their best bet is probably adding teams like Villanova, FAU and FIU and just hoping one of those programs take off.
They also are going to have a tough time adding teams since the more teams they add, the greater the chance of breaking up the basketball Big East conference, which is the flagship sport for that conference. There have been rumors for the last couple of seasons that the non football playing members of the conference have been looking into forming their own conference, if you're adding TCU and schools like that, I see that happening sooner than later.