I don't think CU cuts the mustard of a 10 team Big East. If it goes to 12 they will be right there. Larger than 12 you gotta think they are in for sure.
What if they only go 10 and CU doesn't make the cut but the leftover A-10 is still more attractive and invites CU?
Say for example X, SLU, and one of the east coast schools get in. The A-10 would still haves some combo of Dayton, Butler, VCU, St. Joes, Richmond. Also their is a large amount of east coast non football schools the A-10 could pull from to add with CU. George Mason, Davidson, Drexel, etc.
So to me the biggest danger isn't the Big East itself but a raided A-10 that still has a decent core. I just think that the Big East coming from that giant cluster will want a league that offers true home/away schedule, you never know though.
To me if they leave the Valley needs to be VERY careful on a replacement. Maybe just go with 9 schools instead of 10.