I don't think the Big XII is going anywhere now because its not in TexAss' best interest anymore. Now Texas gets all the benefits of the scheduling stability with a BCS conference - especially for their other non revenue sports as well as the benefits of being an independent with their own TV network. The other BCS league TV contracts are all sewn up once the Pac 12 gets their new deal. The Big Ten, ACC, and SEC all have championship games now so adding another team will only decrease the revenue each school gets. The Big East is the only other option and hell they already have 16 teams for Basketball so I'm really not sure how many more teams they could really add.
I think the other schools in the Big XII are just royally ****ed. Aggy should have gone to the SEC this summer because they missed their chance.
The Big East's contract expires at the end of the 2012-13 year so they will be the only conference that could do anything to affect the Big 12's stability.
With the move to get TCU and their review of other Conference USA schools underway they could decide that the best thing for their conference is to split up the non-football and football teams in 2013, especially if Villanova doesn't upgrade. The football teams will then outnumber the non-football teams (9 vs 8) due to adding TCU so they would retain the Big East name and seat at the BCS table. If they could broker a deal sweet enough, they might be able to get Mizzou, Kansas, and Kansas State to make the jump away from Bevo's harem. Equal revenue sharing in a BCS league with around $6-8 million in annual TV revenue per team might be exactly what those schools could want. The basketball would still be really good with Louisville, Cincy, West Virginia, 'Cuse, and UConn in addition to those 3 midwestern schools. Divisions could be East/West with Mizzou, KU, K-State, TCU, Louisville, and Cincy in the Midwest and the others in the East.
Now, who knows if the Big East would be able to triple their TV $ on a per team basis at that time? Not certain, but the ACC more than doubled theirs in this last negotiation without expanding (it was their 2nd contract since adding BC, VT, and Miami). We are all expecting that the Pac-10/12 will more than triple their per team $ in this next go-round. So, technically it is possible, just depends on the market.
The non-football members (all private Catholic universities) and Notre Dame would then be able to form a non-football league and probably snag some other like-minded schools (Xavier, Saint Joseph's, St. Bonaventure, Duquesne, Fordham, etc.) for a very good basketball league.
The Big 12 would then have few choices but to add teams like New Mexico, Memphis, SMU, or UTEP to retain a 9 or 10 team membership.
If Mizzou, Kansas, and K-State have no desire to talk with the Big East, then I think the Big 12 remains intact for another 10-12 years; when the SEC's 2 major deals get close to renegotiations and then the Aggie and Sooner crowd will put pressure to join once again.