If the big east is completely destroyed (loses AQ status), there will be a massive shakeup out there and it will involve the
current ACC. And that's short term. Long term these schools are going to want to get back to the geographical regions in which they belong anyway.
Pitt and Syracuse are in the ACC now, they're not leaving, at least not for a very long time. If we take Louisville and WVU and possibly Cincy, that leaves just Rutgers, UConn, and S. Florida as fb schools in the Big East. The most likely scenario then, IMO is Rutgers and UConn eventually end up in the ACC putting them at 16 (or ND/UConn if ND's hand is forced) and S. Florida possibly ends up with us (16 with S. Florida, C. Florida, BYU, and ND/Rutgers
). In that scenario where is this viable eastern conference going to come from? None of those teams would be leaving the ACC and I don't see anyone leaving the B10 or SEC so it would have to be formed with teams not currently AQ which isn't going to be strong enough to pull those teams out of the BXII unless it brings along some current BXII teams as well.
I definitely not an expert on the whole conf army thing, but I just don't see a scenario where a new vialble east coast conference appears anytime in the next 20-30 years if the BE is imploded.