stranger things have happened but logistically any alliance, coalition, or scheduling agreement for west coast teams and the ACC has always felt like a non-starter. but to actually join the ACC and commit to playing half your games on the east coast as well as tying yourself to a GOR through 2036?
I don’t know what I’d do if I was in Cal or Stanford’s shoes but I think joining the ACC would be pretty low on the list. Stanford, as a private university with a huge endowment, can do whatever it wants and never notice the loss. They can probably even sell themselves as a legitimate independent and put together decent schedules. But Cal doesn’t have those same strengths.
Off the top of my head: TCU, Houston, Cincinatti and Louisville are four examples of teams which were in the top tier, had to drop to what we now call G5 and have gotten back to the top. It’s not a death sentence to get left out in the realignment olympics. It’s not desirable. But it can be overcome.
Mississippi Valley State @ 
Utah .
