Who goes with them to the ACC, or will the SEC and ACC both have 13 members?
I think it is far more likely that if the Big 12 collapses, UT goes to the Big East who will have their TV contracts renegotiated next year for the 2013 season. Notre Dame's NBC contract runs through 2015 (FYI).
ABC/ESPN already owns most of the Big East rights. They lost some content to Fox and the Pac-12 network effective in 2012, and they also will be losing Conference USA content starting in 2011 (to FSN and CBS College Sports).
They love Big East hoops and have always pushed their football programs like Rutgers and UConn despite luke-warm national appeal.
I think that the there will be a fracture between the football and non-football Big East members, but it might not be such a contentious split if ABC/ESPN softens the blow with a valuable TV deal for both halves, and some OOC basketball games or even a formal series against each other.
The Big East has 9 conference members now that play football plus Notre Dame as independent who could stay in the new conference as a non-football member. Texas could join in the same capacity. Being associated with the conference would give the non-football sports a home, and also help with scheduling issues for football.
Big East would then invite 3 new all-sport members to round out the football membership to 12 teams. Kansas and Kansas State look like locks for 2 of those invites. Missouri will be offered the other, but they could also be weighing an SEC invite. Of course, this all assumes the OU-Okie Lite to Pac-12 scenario occurs. If Missouri gets the invite then you have to figure that a Big East or ACC team gets the 14th invite from the SEC, and if it is the ACC they will turn around and raid a Big East team in return. Meaning, the Big East would have a 4th invite to extend for an all-sports member.
If the Tigers become the third Tiger team in the SEC, then I think Iowa State or Texas Tech gets the invite to the Big East in their place. I think Tech has more pull at this point in time over the Cyclones, especially with TCU and UT involved. Despite their public crying Baylor would not be able to overcome Tech's representation in the legislature.
If the SEC expands beyond 14 then that could open up more spots for the Big East, then you will see lobbying from Iowa State, Baylor, Houston, Memphis, East Carolina, and Central Florida. With the open spots being caused by an eastern team leaving, I can see an argument to add East Carolina or Central Florida to balance the divisions geographically. Iowa State and Baylor would win the academic argument. Iowa State and Memphis would add more from a hoops perspective. East Carolina, Memphis, and Iowa State add new states to the "footprint". Those make a compelling argument that Iowa State could get one of those final invites to the Big East, maybe Baylor gets one as well for a Texas-4 block.
With Texas and Notre Dame adding weight to the basketball and non-revenue sports the conference would be setup pretty solid but probably would not form a conference-owned or branded network.
ABC/ESPN would probably be aggressive about setting Notre Dame up on their own version of the Longhorn Network when their rights came up for renewal.
Texas would then be an "independent" in football with scheduling a lot easier to fit in games against an SEC Texas A&M and a Pac-14 Oklahoma.
They would have TCU and Tech as Big East "members" to work schedules with. Baylor would probably join Conference USA or play as an Indy for a few years but would still jump at the chance to play UT in either scenario. With BYU, Notre Dame, Army, and Navy all Indy there would be opportunity to fill October Saturdays a little easier.
The former Big East basketball schools (Villanova, Georgetown, St. John's, Seton Hall, Providence, DePaul, and Marquette) would then have a 7 team league and would look to invite teams like Xavier, Saint Joseph's, etc. ABC/ESPN could own these TV rights as well to keep rivalry games intact schedule wise and to facilitate getting the football conference wrapped up.
Texas gets to be "special" just like Notre Dame, the 16-team superconferences would probably be avoided, or at least delayed longer than it appears now, and none of it would affect what the Pac wants.