Lots of different angles to consider, but I'd assume nobody from the PAC makes a move until there are firm offers for their new media deal.The only way they would renegotiate the deal would be if someone joins/leaves. But that is separate from the GoR. With that there is nothing that says they will substantially increase the deal, rather it could be just increase/decrease the pay by said number of teams joining/leaving. For instance just add the current rate of pay for someone joining.
But any team that joins the ACC is required to sign on to their GoR Until 2036.
I'm guessing the numbers aren't going to be great. I could be wrong - maybe Amazon, Apple or Netflix is willing to pay a premium to get into college football. CBS might really not want to get shut out of college football. Maybe NBC wants to have more content to put around Notre Dame games. But I would not expect Fox or ESPN to pay a premium for the PAC.
If the race is on for the #3 conference, the race is on for who gets to broadcast it. That means the Big XII and ACC are (most likely) going to compete to get a few PAC members. I could see ESPN being willing to re-negotiate the ACC's deal, or Fox trying to lock down the Big XII early, but each trying to out-do the other.