Oh, for us at least, if it's full membership, it's the best of all reasonably possible worlds.
1) We get keep our existing relationships with Big East teams that we love playing;
2) We get to reunite with our wayward Big East brothers with whom we had good rivalries going back in the day;
3) We get more games against schools that value basketball like UNC and Duke;
4) We get bowl the bowl affiliations and easier scheduling of being in a P4 conference; and
5) P4 money, which in the ACC, though much much less than the P2 make, is significantly more than we currently make in the Big East.
That said, I'll believe it when the papers are signed. It makes some sense because the ACC has become the most vulnerable of the P4, so that may open up their willingness to merge. Given their current basketball challenges the Big East must seem attractive to them. The devil is in the details though. They'd have to be willing to significantly up the payout to the basketball only schools to make it worthwhile. I have a healthy skepticism that they're willing to do that.