It's a bulletin/breaking news type of story, but in a way I'm not surprised. I predicted that he would step down after Jay Leno "retired." Dave wanted to be the last man standing, and hold the record for "longest serving host in Late Night history."
First off, I'm a huge fan and he was my generation's beacon for broadcasting. Lately, however, the show has become stale. Dave stopped doing field pieces himself, (which was one of his strengths and provided some great television) and let staff members or comedians do them. I think his heart isn't in the show anymore, and he alluded to that on Thursday night.
Also, this isn't a spur of the moment thing. The "Letterman Retirement" scenario has been worked out for a while between Worldwide Pants and CBS. It has to be. If there was an emergency and something happened to Dave, there is a protocal for a transition. The surprise is that Dave called Les Thursday at 5:00 from his office and said that it's time. He was probably mulling this over for a few weeks.
That being said, Craig Ferguson will probably be named his replacement. A Right of First Refusal clause was written into his last contract with Worldwide Pants. That means that he can refuse the 11:35 show if he desires. That contract expires as the same time as Letterman's. I believe that it was written to prevent what what happened to Dave in 1991 when Johnny Carson announced his retirement from the "Tonight Show." Letterman feels that he doesn't want anyone else to go through the hell that he did when NBC went with Leno instead of him.
Conan O'Brien WILL NOT be offered the show. He's a great talk show host, but it serves a niche audience and that is a strength of TBS. Conan's show is great for cable, but it won't play on CBS at 11:35.
Chelsea Handler WILL NOT be offered the show. Reason: She's Joan Rivers 2.0. Word came out last night that she has been in talks with CBS for some new projects since her contract is up with E! She may be offered the 12:35 slot.
Jon Stewart MAY be offered the 11:35 slot. His contract with Comedy Central is up next year, and that is part of the Viacom/CBS/Westinghouse family. The question is can he deliver the numbers for CBS and compete with the Jimmys? Maybe, but remember, the host of the Daily Show that Jon Stewart replaced: Craig Kilborn. He had a great show on CBS, but it didn't translate and served a niche audience.
The likely scenario is that David Letterman will step down during a sweeps period, most likely May 2015 (with Bill Murray as his final guest and maybe an appearance by Harry Letterman sometime around then). Craig Ferguson will become the host of "The Late Show with Craig Ferguson" from Televison City in Los Angeles. Yes, CBS will move the show to California. They want to draw on the talent that's still in Hollywood. It will be strong being that Ferguson doesn't do a conventional talk show. He does conversations (i.e. no notes and will have folks on who don't have anything to plug) and his doesn't do a joke-joke-joke monologue. It is a single topic monologue. The 12:35 slot is up in the air, but I have a feeling that it will go to Chelsea Handler.
Of course, this is all conjecture, and it's my opinion, but this seems to be the likely scenario.
It will be intersting to see what happens. Somewhere in New York, Bill Carter is already writing the rough draft to his third book about Late Night Television.