The B1G12 has always wanted Virginia and UNC. It's been a long running thing for them. They even wanted Georgia Tech and Duke. I'm not sure what happens to little brothers NC State and VT in such a situation, but I'm projecting they get left behind. FSU, Miami, Clemson, 2 of these will join the SEC.
I see 5 (including ND) but possibly 7 (including ND) teams leaving the ACC.
UNC, Duke, ND, Virginia to the B1G, FSU & one of Miami or Clemson to the SEC.
Left behind: Pitt, BC, Syracuse, Louisville, VT, NC St, WF, GT to the ACC. They could backfill with WV and USF and then leave it at that, but I doubt it.