According to this, and it's been picked up by a lot of media outlests, the Big 10 has offered Notre Dame, Rutgers, Nebraska and Missouri.
The idea is that if Notre Dame refuses, they stop at 14 schools at least for the moment. If Notre Dame accepts, they will offer one more invitation and go to 16.
My thoughts are that almost certainly Notre Dame will reject this. Losing Rutgers is not enough to decimate the Big East in my opinion, which leave the Irish a place to play their other sports. If that comes to pass, this is probably decent news for the ACC.
Several schools that would have to be ACC targets in an ACC expansion were not invited - Pitt, Syracuse, UCONN, WVA (well, we knew they weren't going to be invited). I really like having Pitt still in play as this stuff shakes out. In addition, dark horse Big 10 candidates BC and Maryland didn't suprise us by being on the list.
If the ACC is forced to go to 16, it could have been much worse if those schools had been off the board.