Leno is obviously pissed at the publicity that NBC will replace him with Fallon. This news should not be a shock to a guy who was replaced by the 12:35 guy just a few years ago. NBC needs to check their short term memory. Moving Leno out of 11:35 did not work. The ratings are not going to up if Leno leaves. Even though Fallon is a better fit for "The Tonight Show" than Conan was, it's still a new show. It is still something for people to get used to.
Even an edgy Leno is a dull Letterman.