Again: if they didn't leave back when Texas was acting super prima donna, they're not leaving now.
Where would they have gone? The schools that were able to get invites split. After Nebraska and Colorado got out, Oklahoma had worked out a deal with the Pac 12 to move themselves, Okie Lite, and the four original Texas schools. But, that fell apart when Texas worked out their deal with ESPN. That led to A&M and Mizzou taking off. With Texas standing pat, where else could any of the other teams get an invite?
As it stands right now, Texas basically operates as an independent inside its own conference, and no other league is going to let them do that. Oklahoma would be attractive, but they would have to separate themselves from Okie Lite, and that brings political issues. No one is going to take both Oklahoma schools. Where else is there any value?
There is no "splinter risk" in the current B12.
That's true for the moment. But the league's media rights deal expires in 2025. There is no way that ESPN is going to re-up the Longhorn Network. Are Texas and OU going to throw their third tier media rights in to sweeten the pot for a standalone conference network? Even if they did, would it be worth it to Disney or Fox?
I could see the Mountaineers finding another home that fits better at some point.
Where's that fit? Which of the remaining big 4 would take them?
Outside chance it grows, back to 12.
Who would they add? They already flirted with expansion a couple of years back. The candidates were so awful that Fox and ESPN paid the league a few extra million to avoid having to pay $20MM+ to Houston, Memphis, or Cincinnati.
The Big XII is only going to last as long as Texas needs it to last. If the media rights deal is greener in some other yard come 2025, Texas is gone, and the Big XII either drops to G5 status or dies all together.