The Grant of Rights would have to be changed and changing it would be a money loser for most of the ACC schools. I can't see it.
With the Grant of Rights in the ACC, any school that leaves STILL owes the ACC their media money until 2036 even if they aren't in the conference. If FSU joined the SEC, they'd have to give their SEC media money to the ACC until 2036. That's an enormous ball & chain, even if they agreed to it just to get out.
Schools like Boston, Syracuse, Va Tech, etc have nowhere to go and earn ACC money. I can't see them voting to cut the money their athletic department makes.
The NCAA has spoken, though. Only the SEC and B1G actually matter in football.