Will Letterman leave 'Late Show' in 2013?

First, Regis. Now, Dave?

Amid the jokes, laughs, and Jay Leno jibes in last night's hugely amusing David Letterman/Howard Stern encounter, there was this bombshell: Letterman says he'll leave "Late Show" in two years.

Letterman's brief response to Stern's question -- when will you leave -- was the first time in his long career that he has directly, specifically (and apparently seriously) addressed the question, at least on TV. He has said he'll finish his career at CBS and has joked about retiring. But there was something different about last night. 

Rob Burnett, president of Dave's production company Worldwide Pants, downplayed the remark in a phone interview.  "Dave and Howard are very rare entities in show business in that most people are asked to leave the stage. These guys have complete control over their own exits." Nevertheless, he said last night was not a formal announcement: "Dave has mused on air about retiring lots of times. Whenever the day comes that he actually chooses to announce his departure, I don't think that announcement will be ambiguous."

Dave turns 64 this April, which means he'd be leaving -- if he does leave -- at age 66, when his role model Johnny Carson stepped down. 

Here's another question, that begs asking: Will Jay Leno leave before then, as many have speculated, giving Dave a chance to go out on top? There has been some internal discussion at NBC about the eventual succession of Jay Leno -- yes, Jay will step down some day, too -- and whether he will be replaced by Jimmy Fallon. Fallon is very good but there's no doubt he would lose viewers who were more used to Jay's homespun cornbread Middle America humor. Then: Could Dave's numbers surge again, as they did when Conan O'Brien stepped in? That has to be a consideration at CBS too, but may well mean that Dave -- if he does leave in two years -- could leave on top, just as Johnny did.

How did Johnny announce his retirement? Not in a news release, and I assure you: Dave wants to announce his departure date on his own terms, too. Johnny stood on the podium at Carnegie Hall and on a beautiful May day in the early '90s, he said he would step down. It was a mind-blowing moment at NBC -- completely blindsided -- but Johnny was gonna do it his way. Dave is gonna do it his way, too.

Check this clip: 2:45 in. You heard it here, from Dave's mouth, first. A TV legend may well have just announced his retirement last night.