We will also witness two of the last great vestiges of baby-boomer culture leaving the main stage of American life. Say goodbye to the Me Generation and all its generational chauvinism, its no-decade-was-greater-than-the-'60s attitude. As far as TV and all the little screens that now surround it are concerned, no one much cares anymore how Ed Sullivan or the Beatles or "The Flying Nun" shaped the lives of these postwar children — or didn't.
Born in 1947, Letterman has long been the guys' comedian for that generation — for better and for worse.
Better, in the way he took a pop culture that worshipped the show-biz glitz of Johnny Carson's "The Tonight Show" and made viewers smarter about the artifice behind such TV creations. Letterman's brilliance as a performer resides in the way he mastered the desk-and-couch talk show genre and then deconstructed it with mockery, irony and snark.
Letterman didn't invent irony, but he was at the forefront of a movement that helped make it the dominant sensibility of American entertainment programming — and now life. All that snark and irony on the Web and social media? You can thank Letterman to some extent for that.
I am not so sure any of that was for the better.
For baby boomers feeling suffocated by their Greatest Generation parents' unquestioned platitudes and beliefs, a little irony and derision was certainly a healthy antidote — an attitude that fit their "question authority" mantra, especially in late-night TV.
But for millennials who have never known anything but the sarcasm of "The Simpsons" or "South Park," is there anything in which they can wholeheartedly believe without feeling naive or silly — or worse, primed to be mocked on social media?
Letterman influenced the current generation of late-night hosts. Jimmy Kimmel, Conan O'Brien and Seth Meyers acknowledge their debt to him, with Kimmel calling Letterman's show "the most formative thing" in his life.
Without Letterman, it's possible that there might not have been a Jon Stewart. The departing Comedy Central star borrowed attitude from Letterman, though he took it in a political direction, which is something for which Letterman has far less aptitude.
Mainly, like Jay Leno, Letterman allowed his couch to become a haven for politicians looking to dodge a questioning press while delivering their spin straight to millions of viewers under the gaze of a chuckling host. It was politics as entertainment — and the last thing the nation needed was more entertainment and less reliable information about our elected officials. But Letterman gave us that, too.
And that's the upper end of Letterman's influence. The lower end involved giving baby-boomer men a way to be silly or stupid and think they were cool. In one sense, this is as harmless as his stupid pet tricks.
But Letterman's influence on baby boomer masculinity runs far deeper than that. Just as Carson defined a certain kind of Rat Pack booze-and-broads masculinity for his late-night audience of men, so did Letterman for his. It wasn't as culturally noxious as Carson's, but it was definitely sexist.
Cher, Madonna and Courtney Love have all had on-air run-ins with Letterman that involved them calling him a jerk in one way or another. (Just typing those names serves as a stark reminder of how long Letterman's been on the air.)
But it is his 2009 acknowledgment that he had sexual relationships with female interns that continues to define his attitude toward women in my mind.
Despite the battles fought by baby-boomer women for equality in the workplace, some boomer men have been very slow to sign on to gender equity. Letterman's gross misuse of power is not on a par with Bill Clinton's while he in the White House, but it is made of the same sick stuff as that of our first boomer president.
These finale pieces are supposed to be full of only the good stuff about a departing performer or artist. But I have never believed that it is acceptable to shade the truth as a journalist, even in an appreciation.
One final boomer touch: Two of Letterman's last guests will be 64-year-old Bill Murray, who also was his first in 1982 on the comedian's NBC show, and Bob Dylan. Nothing says boomer quite like Dylan.
I have always been honest about my feelings toward "Mad Men," which has made my history with it a roller coaster ride.
During Season 1, I adored this slick look at life on Madison Avenue in the 1960s. After watching "The Wheel," the final episode of that season, I thought the AMC series might be the greatest TV drama I had ever seen.
That's the episode that features Don Draper (Jon Hamm) making a speech on memory and nostalgia in connection with his client's product, a photo projector carousel (The Wheel). His pitch for the Kodak-like product is so smart and deeply moving, you think the screen is going to explode from an overload of wisdom and emotion.
My TV love lasted through all of Season 2. But then, instead of the Existential Don, who so richly appealed to me as the character in a great novel might, we started getting Magazine Cover Don, which was all about clothes, sex, good looks and the commercialization of this series. Banana Republic meets Brooks Brothers, and I hated it.
To his credit, creator Matthew Weiner has resurrected Existential Don down the home stretch, leaving Draper last week at a bus stop in Oklahoma — all the glamour long gone.
As a result, not since "The Sopranos" have I been so amped up to see how a series will end. And I have no idea what that will be. Will Draper follow the east-to-west movement of American life and wind up in California sitting at the dock on the bay? Or will he return to the East and try to pick up the pieces of his lives? Weiner wouldn't leave Draper out there on the merciless plains trying to atone for his sins like some monkish penitent, would he?
Even though Weiner, who was born in Baltimore in 1965, is not technically a boomer himself, I can think of no series more steeped in that generational sensibility, thanks to its '60s setting.
And no series has so supported the boomer core belief that everything you ever needed to know about 20th-century American life could be learned by studying the '60s.
"Mad Men" absolutely wallowed in '60s nostalgia — even as it commented on the excesses and failures of the age. Boomers will never see another TV series so in sync with their narcissistic view of American history and life.
Look around: There is not much boomer identity and culture left on TV. Even "CSI" is going away with its 67-year-old star Ted Danson.
Typical of the transition on the news front: Diane Sawyer stepping down last year at the ABC anchor desk to make way for 41-year-old David Muir. Or how about 44-year-old Megyn Kelly on the verge of eclipsing 65-year-old Bill O'Reilly as the biggest star of prime time on Fox News? And Fox is a network geared toward boomers — and anyone from the Greatest Generation who is still watching TV.
Given the extent of that shift in demographics, I wouldn't want to be a 67-year-old presidential candidate who has to maintain her predecessor's hold on young voters to get elected.
But maybe Hillary Clinton can beat the odds — even as her generation moves from dominant to marginalized on the biggest stage in popular culture.
The finale of "Mad Men" airs at 10 p.m. Sunday on AMC.
David Letterman's last show airs at 11:35 p.m. Wednesday on WJZ-TV (CBS).