Something NBC and Jay Leno may not realize is that, no matter what the reality is, whether it's a decision by Jay Leno or NBC execs or blah blah, that's not how it's going to play to the viewer. The viewer will probably think Jay Leno is personally robbing Conan of something he was promised 5 years ago. And that will affect ratings in the long term and create a an audience that wil leave NBC to go watch Conan's show (Ugh, please not Fox. I hate Fox.)
It's extremely short-sighted of them to trade away somebody who plays for a younger crowd so you can get a definite, yet shrinking audience.