Jay Leno exits. Jimmy Fallon succeeds, or not. Late-night lives on.

As Jay Leno prepares for his final "Tonight Show" monologue, the overall ratings for the venerable NBC show are a fraction of what they were in 1992, when he took over from Johnny Carson.

But the numbers belie the continued importance of the late-night landscape as it has fragmented over the past two decades. While one show may no longer dominate as it did back when Mr. Carson was considered a kingmaker for young comedians, the collective world of late-night comedy from Jon Stewart’s "The Daily Show" to Stephen Colbert and Jimmy Kimmel remain vital in the popular culture, say media-watchers.

“People may be fond of saying the broadcast networks are dinosaurs left over from an earlier era,” but the 11.9 million viewers who tuned in to watch Leno this week is still a healthy audience for any era,” says Robert Thompson, founder of the Bleier Center for Television and Popular Culture at Syracuse University in Syracuse, N.Y. And while the numbers for this week are not the norm, he points out, “all these late-night shows together matter, whether it’s David Letterman, Craig Ferguson, Jon Stewart, Seth Myers, or Jimmy Fallon," for the simple reason that together they still play an important role in popular culture.

“If journalism is the fourth estate that keeps the government in check,” then the vast amount of dialogue these comedians generate in the popular culture “makes them the fifth estate, keeping journalism in check,” says Professor Thompson.

While we're long removed from the days of a single late-night host and franchise being able to set the national humor agenda, late-night programming "still matters greatly both to networks and advertisers because, quite simply, people still watch late-night TV,” e-mails Jim McKairnes, Verizon Chair at Temple University's School of Media and Communication in Philadelphia.

And, he adds, they then “talk” about it, in all the various forms of social media from Twitter to Facebook, “which is even more important.”

It still matters to culture, too, he notes, “if evidenced only by the very coverage this transition is getting in both traditional and New Media.”

If numbers aren't what they were on a show-by-show basis, the aggregate viewership demonstrates a still-more-than-healthy interest on the part of consumers, Professor McKairnes says, “especially on the part of those appealing younger ones who gravitate towards the kind of social-media-packaged humor that the likes of Fallon and Kimmel offer so well.”

"Beyond 'Breaking Bad,' when's the last time a prime-time show – or a digital one, for that matter – was connected to a viral clip like Kimmel's twerking-video prank or like Fallon's 'All I Want for Christmas Is You' duet with Mariah, now a perennial holiday staple?" he asks.

Indeed, late night remains a huge area for growth, both creatively and financially, says Dennis Mazzocco, a longtime TV director and producer and a professor of radio, television, and film at Hofstra University in Hempstead, N.Y. Besides the simple revenues to be gleaned from this relatively cheap programming, which can be considerable for both network and local affiliates, there is the added value for promotion of other network programs and other media properties that the networks' corporate parent may own, points out Professor Mazzocco.

However, passing the torch to younger comics who appeal to the younger demographics is still tricky, he adds. CBS needs to worry about how long David Letterman can compete against the two Jimmys – ABC’s Kimmel and the incoming Fallon at NBC, he says.

Some suggest the newly anointed Fallon faces serious challenges, as well. The talk shows we see on network television are remnants of a time when audiences placed their "trust" on TV personalities, whether newscasters such as Walter Cronkite, or entertainers like Carson, and people had the patience to watch other people talking to each other, says Mario Almonte, PR specialist and blogger on politics and popular culture at The Huffington Post.

Today, he says via e-mail, shows are less about personalities and more about fast-paced entertainment. “Popular shows like 'The Colbert Report' and 'The Daily Show' are heavily edited, with a great deal of flashy videos, camera moments, quick interviews and even quicker commentaries,” he says.

For all his talent, Fallon is basically doomed to fail on "The Tonight Show," says Mr. Almonte, “for the simple fact that his core audience is not into 'The Tonight Show,' so they won't follow him there. The current 'Tonight Show' audience is already predisposed to having a negative opinion about Fallon, and so will stop watching the show or gravitate toward Letterman, whom they are familiar with from a long time ago.”

Others see his skills with new media and proven pop culture popularity from his tenure at Saturday Night Live (SNL) as signs that he will make the leap. Fallon is a good choice for a number of reasons, says Leonard Shyles, professor of communication at Villanova University in Philadelphia. He is a leading sketch comic featured on SNL, an NBC franchise winner for decades. And “he works hard,” notes Professor Shyles. His monologue is improving, “though he can get even better," says Shyles, who predicts a successful transition this time, as opposed to when Conan O’Brien tried “and things did not work out.” 

Details of each transition aside, however, the overall prognosis for the late-night landscape is healthy.

“Late-night still drive chatter, still stirs up conversation, still attracts eyeballs, and as a result still adds up in the credit column,” says McKairnes.