There are currently 3 ACC teams in the top 12 rankings (Miami, SMU, Clemson). For the sake of argument, I'm going to count Notre Dame as well since they share ACC bowl tie-ins, and area member in every other sport. So let's just say 4.
Best case scenario for the ACC: all four teams win out, SMU wins the ACC title game. We would have 12-1 SMU, 11-2 Miami, 10-2 Clemson, and 11-1 Notre Dame.
In this scenario, I think all four get invites. SMU gets a bye, Miami would have a high profile Heisman finalist, Clemson would have a very similar resume to Tennessee for example (both lost to Georgia, Tenn beat Alabama and Clemson over SC), and Notre Dame, despite having one bad loss, has plenty of other good wins like A&M, Army, USC.
Now the opposite scenario:
Everybody loses. Cal over SMU, USC over ND, SC over Clemson, Syracuse over Miami.
Clemson goes on to the championship game and wins. Clemson gets the auto-bid, at 10-3. It is questionable as to whether any of the remaining teams get an invite. Possible, but probably coin flips for everybody.