I reiterate,
The Big 12 wants/needs 10 teams for 2012.
2 schools can give that to them, TCU and BYU.
Right now the decision by Missouri has a lot more bearing on the future of BYU then the inclusion of TCU.
Take
a

The deadline for Missouri being able to leave the conference before the start of the 2012 season has come and gone (Texas A&M left right before the deadline). If the Big 12 wants to keep them in the league until 2013 it is still their choice. However, BYU is still the only team that can join for the 2013 season if the Big East is around to enforce their 27 month notice rule. If the Big East implodes there will be five teams available for the 2013 besides BYU.