I think it's easy to overestimate the importance of short term football success relative to conference success. You can still make a lot of money even if your teams are not especially successful. Having said that, the ACC was, and to some degree still is vulnerable due to being top heavy in football and really controlled by the basketball schools.Other than Clemson, the ACC last year was mediocrity at best, and a garbage fire at worst.
After the Big 12 managed to survive, the ACC was the next vulnerable conference. They lost Maryland, and there was some talk of Clemson and FSU to the Big 12. The additions (partial in ND's case) of Notre Dame, Pitt, Syracuse, and Louisville stopped the bleeding, but really only one of those schools did much and they're not a full time member.
If they lost Notre Dame, that could mean losing an important crutch. Right now though, there's only two rock solid conferences. The SEC is #2 in revenue but with a big deal coming up that could in theory put the SEC at double the per school payout as the lower power 5 schools. The Big 10 is #1 and will be at worst #2 for the foreseeable future.
The Big 12 got a sweetheart deal to keep them alive, so they're sitting at #3 and one reason it's not absurd to suggest they add a Pac -12 or ACC school (they're also geographically in the middle).
The Pac-12 is #4 and the ACC is #5 with a deal that seems to favor the basketball schools.
Ironically, one reason the Big 12 is relatively safe is that aside from Texas I'm not sure any conference really wants their schools. Meanwhile, the Pac-12 has USC, and the ACC has Clemson, FSU, Notre Dame (sorta) and North Carolina (a massive basketball school in a big state).
I don't know what happens next, but if the SEC gets a deal the size that has been reported, and they are paying their schools 30 million more than the Pac-12 and over double what the ACC is paying, that could make a lot of schools unhappy...