I'd be surprised if they don't end up with him in the end, but I'm not counting out the Rangers and the Angels from making a legit run at him. From all accounts, Lee enjoyed his time in Texas immensely and playing within a few hours of his home in Arkansas was a major bonus as well. If the Rangers give him a 7 year deal he's in the bag... a 6 year deal with bigger numbers would probably do it as well. At the very least I suspect he'll let the Rangers have a chance to match whatever the Yanks throw at him.
The Angels are intriguing as well. Add him to the top of their rotation, and they're looking really good with Haren and Santana behind him. Their offense would lack the firepower the Rangers have, but a healthy Morales and a few role players could solve that. Plus that kind of staff would have the ability to shut down opponents enough that it wouldn't matter.
That said, I'd be ecstatic if the Sox went all in and got him. Our rotation would be beyond belief.