I'd be shocked if Texas/OU stayed in the Big 12 that long. Can't think of a time where a school ever said they were leaving a conference and then stuck around for four more years. It's better for all involved if they leave sooner than later.
Taking away the Texas/OU voting rights would give them a legitimate legal argument that the Big 12 is violating their own bylaws. Then the lawyers get involved and it's much easier for Texas/OU to leave early without paying any exit fee. The Big 12 bylaws state a 75% vote is needed to make changes to conference membership so if the remaining 8 are all on board then the votes of Texas/OU don't matter. The 2 problems that arise then are:
1. Do they really want Texas/OU involved with any conversations surrounding future conference membership? Texas/OU will be privy to that information, and the Big 12 may not want a departing member to know inside information on future plans.
2. Can the Big 12 last 4 years where all remaining 8 conference members are on board in an uncertain environment? That's a long time for 8 schools to stay in lockstep. Especially at a time when any of the 8 would jump at a chance to join one of the remaining Power 4, and the league was just blindsided by the departure of it's anchors. If they lose one more they no longer have the 75% vote needed.
Here is an article about it:
http://www2.kusports.com/weblogs/tale-tait/2021/jul/28/ou-and-texas-should-pay-to-leave-the-big/
This pretty much sums it up:
"But if the plan is for a revamped Big 12 to move forward with new members, then perhaps some kind of settlement so all parties can move forward more quickly is actually in the best interest of the Big 12 Conference.
After all, when the existing grant of rights contract expires and it’s time to negotiate new TV deals, stability will be your friend and uncertainty can cost you millions."
Texas and OU will be SEC members by the time football season kicks off in 2023 at the latest. Something will be worked out with the exit fee.