1. Expansion/realignment doesn't happen that often. 2010-2013 was a bunch of realignment. And then not again until 2023-2025. So it's possible things sit relatively stable for ... say 8 years. And then by 2031, it's a lot easier to talk about ACC teams.
2. The ACC GOR may or may not be ironclad - very little ever is. If Miami or Clemson or Florida St can make 2x as much by going to the SEC (or Virginia or UNC to the Big 10) you know they have teams of lawyers looking at ways to get around things