I have a bit of a different perspective on this. I don't think Colorado (and possibly Arizona) are running to the Big12 as much as they are running away from the PAC. It's quite probable they are doing so because they feel that the departures from the PAC are not over. The loss of USC and UCLA were absolutely huge and if you believe some combination of Cal., Stanford, Oregon, Utah and Washington are at risk, then you have to make the move. Now couple that with the eventual departures from the ACC as the GOR nears expiration and conferences on both coasts are in upheaval.
This is going to be a long game and UCONN probably doesn't move this year. But within the next ten years there will be the BiG and SEC at a different level than everyone else (at least in terms of money). My hope is that the other conferences will restructure along some lines of regional alliances.
FWIW, if the choice for the Big12 is between Arizona and UCONN I don't see UCONN winning that bake off.