Georgetown
Marquette
St. John's
Seton Hall
Providence
DePaul
Villanova*
*Villanova seems likely to upgrade their football in the face of all of this tumult, although admittedly I have not followed their thinking very closely.
That is your Big East conference once all the football teams find other homes. That is not only too small of a conference to survive, but it really isn't very good, either. If Villanova goes FBS in football, I could see Georgetown and Marquette going to the A10, which has recently added geographic rivals VCU and Butler and is now unquestionably the best basketball-only conference in the country. Playing in a 16 team league that is already established against teams like Xavier, Dayton, Butler and VCU would seem a much better option than playing in a six team start-up conference with PC and Seton Hall.
If that is the case, Notre Dame should, and probably would, end up in the Big XII, at least for non-football sports. They could have the same deal with the Big XII as they now have with the Big East, playing 3 or 4 games a year against Big XII schools. That would appeal to me.