What kept NBC from keeping Conan and letting Leno walk back when that whole "thing" came to pass was Leno's contract. NBC made a decision based on counting the beans. Letting Leno leave meant paying him a lot more than they'd have to pay Conan so they let Conan walk. If Conan's ratings had been higher, they might have opted to let Leno leave and just take the financial hit, but with sinking ratings, and a lower cost to keep Leno, NBC just let Conan go. That contract that was in effect when faced with that earlier choice is coming to an end. NBC can extend that contract and lock themselves into more time with Leno (which could mean lower ratings throughout the contract), or they can pay a much smaller fee for kicking Leno to the curb, if they pay anything at all (depending on when they make a change over to someone else). As noted by others here, Kimmel is giving Leno and Letterman both a good run for the money in the ratings, especially in key demographics and that will likely continue to get worse as the Leno fans are aging quickly. Leno may not want to leave, but he may find himself without a home, or at least without the old Tonight Show home. It could get very interesting to see him having to go off to another net or cable channel.