David Letterman’s surprise announcement Thursday that he will vacate CBS’s “Late Show” chair sometime in 2015 once again sets in motion a favorite American guessing game about the future of late-night television.

Letterman’s lasting contribution to popular culture is the cynically pregnant pause that follows: Television? Nobody’s watching television anymore! What’s a late-night show in a culture that watches tiny bits and pieces of it the morning after?

That’s Letterman’s greatest skill — convincingly pretending that his three-plus decades and counting on bedtime TV (21 of them on CBS) have been a happy accident that somehow goes out over the airwaves night after night; it’s all been an egregious programming mistake, about which the host is eternally humbled and awfully sorry.

Letterman’s idea of fake humility, rooted in what has always appeared to be a Midwestern sense of self-deprecation, is infinitely preferable to new “Tonight Show” host Jimmy Fallon’s idea of fake humility, which appears more and more to be rooted in the vacuity of show biz, where the kissing-up never stops. (Happily, the host of ABC’s “Jimmy Kimmel Live” seems unburdened by any need to project false humility. Because it’s funnier that way.)

But Letterman’s aw-shucks nature is not all viewers will miss after the host leaves. As it’s played out, Letterman is the lone grown-up in the broadcast networks’ 11:35 lineup and one of the last hosts anywhere who can engage in what was once known as a light conversation with anyone from freshly hatched starlets to elder statesmen.

A light conversation is not a competition between two people trying to outmaneuver each other, as viewers occasionally see on “Kimmel”; nor is it a clever pantomime of a conversation built on the post-irony of our mutual disdain for media (Comedy Central’s “The Daily Show with Jon Stewart” and “The Colbert Report”); nor is it a preliminary and fawning bit of chitchat that is merely an overture to a game of beer pong or a balalaika-flute jam between Vladi­mir Putin and Sarah Palin — or whatever set of antics Fallon so clearly prefers to actual talk.

Who should replace Letterman? Rumors fly — and quickly flocked Friday to the enormously talented host of “The Colbert Report,” comedian Stephen Colbert, 49, who since 2005 has kept aloft a neocon news shtick long past the George W. Bush era it was meant to lampoon. “The Late Show with Stephen Colbert” is admittedly a tantalizing and easily envisioned idea, in which the “Colbert Report” persona would be ditched in favor of a disarmingly funny late-night host.

There’s also an heir apparent, perhaps only in a very technical sense, in 51-year-old Craig Ferguson, who has hosted CBS’s after-Letterman “Late Late Show” for nine years now. Ferguson’s show often exhibits the signs of mania that accompany the fear that nobody is watching. Whether he wants the job or not (or whether CBS will find some way around the protocol of offering it to him), Ferguson’s conversational skills can often be top-notch. (Disclosure: I appeared as a guest on “Late Late” in 2009 when I was promoting a book.)

Should it be a woman? (Ellen DeGeneres? Chelsea Handler?) Should it be someone who isn’t white? (W. Kamau Bell, perhaps? Chris Rock?) Should it be someone who upsets convention? (Bill Maher?) Should it be someone who is most like Dave? (Conan O’Brien? Or Louis C.K.?) Or someone who is the least like him? (Jay Leno — LOL + sad tuba bleat. After all the ink and all the ballyhoo, wouldn’t that outcome serve us right, in a culture that can’t stop making sequels?)

It’s exhausting, making a decision on which we’ll never have any real influence. I’d quietly hoped — and perhaps you had, too — that we’d get at least a year or two of relative calm on the late-night front, enough time to see if Fallon, who will soon turn 40, can sustain the impressive ratings he’s been earning since “Tonight’s” relaunch a mere six weeks ago.

Lately I find myself preferring to watch Kimmel, 46, who traces his desire to be a late-night host back to his teenage years when he would faithfully watch and admire Letterman. Kimmel has steadily and sturdily built a show that appeals to both younger and older audiences. Whatever pleasure I drew from Fallon’s first few episodes of “Tonight” quickly cooled; the show’s youthful energy has become a frenetically grating birthday party that never ends.

Although Letterman presented his retirement to his viewers as a personal decision — couching it in a sweet little story about a fishing trip with his 10-year-old son — anyone who’s paid attention to the late-night wars over the years knows that it also has to do with ratings and the network’s bottom line. It’s likely that Letterman and CBS look at Fallon’s ratings as a wearying challenge; after some 6,000 broadcasts, it’s just another climb up a less attractive mountain. The tweeting, the viral ­video-making, the constant need for fresh buzz — who needs it, at his age?

Letterman, a leading-edge baby boomer, turns 67 next week. That’s retirement age in an ideal world, even if boomers don’t like to be told when to hang it up. As opposed to his 63-year-old rival Leno, who transmitted his resistance to being shown the door once more, Letterman has a Johnny Carson-like opportunity to show an American audience the value in stepping aside and handing off an important piece of our popular culture to the next generation.

I hope that the person who gets his job will, in turn, present a show that looks and feels as if it belongs on CBS. That doesn’t mean old, but it does mean something ineffable and increasingly impossible to describe in an era in which all media formats are in a state of reinvention. I’m simply hoping for a “Late Show” host who knows what it means to be a funny adult.

Viewers like me who have been watching David Letterman for three decades can at long last relate to the ever-fainter nostalgia of Jack Paar fans. You know the usual refrain: An era is going away and taking something with it, and so on and so forth — the very sort of sentimental pap at which Letterman would pretend to mockingly grimace. In the next year or so, I hope he continually reminds us that it’s only television.


Late Show with
David Letterman

(one hour) airs weeknights at 11:35

on CBS.