I don't think it was a bluff, but when they started talking to the PAC 10 officials, they probably weren't getting what they wanted, which was to have control or a good bit of control like they did in the Big XII. The Pac 10 probably wasn't going to let them have their own TV deal, among other things. I think Texas basically found out that they don't have all the lead in their shorts that they thought they did, and decided to "save the Big XII, so that they could look like the good guy and the other teams would owe them that much more.
Eventually, Missouri, Oklahoma, Oklahoma State, or all the above, is going to get fed up with Texas again. When that happens, look for them to leave, and that will be what brings the league down. There will be a mass exodus. Another thing that could bring this on is if the SEC and the PAC 10 start expanding - nobody is going to be in a position where they can't get into one of the envisioned 4 super conferences. I think if Oklahoma and Oklahoma don't leave now, they are making a huge mistake. Missouri, if they ever do get an invite to the Big Ten, should just keep their mouths shut and take it, instead of waving it around and trying to play hardball with the Big XII like some kind of think they may have been doing (without actually having an invite - DUH!).