Is the end of late-night TV as we've known it near?

Late-night television could be facing seismic shifts as trends that have shaped the industry during the past few years take an increasing toll on two signature network shows. 

First, ABC has announced that it will move “Jimmy Kimmel Live” to 11:35 p.m. starting Jan. 8, pushing the "Nightline" news show to 12:35 a.m. 

Second, NBC’s “Tonight Show” – long the lucrative late-night standard-bearer – laid off 20 employees in August and host Jay Leno took a 10 percent pay cut. The Los Angeles Times reports that the show is “barely breaking even."

For some media experts, it raises questions about whether the three pillars of late-night television during the past 20 years – "The Tonight Show," "The Late Show with David Letterman," and "Nightline" – are nearing their expiration dates, at least in their current forms.  

Cable now controls 84 percent of the $5.6 billion late-night TV market, according to Kantar Media research. In 2011 alone, broadcast TV's share of late-night viewers fell 5 percent.

For "The Tonight Show" and "The Late Show," perhaps the bigger issue is the demographics of who is watching. Jon Stewart of Comedy Central's "The Daily Show" is attracting more viewers aged 18 to 49 – the demographic most sought by advertisers – than is Mr. Leno, and Stephen Colbert, whose "Colbert Report" follows "The Daily Show," is close.

"The Daily Show" has a median viewer age of 43, compared with 58 for "Tonight." (By comparison, the CBS news magazine "60 Minutes," one of the oldest-skewing shows in prime time, has a median viewer age of 61).

That was what moved "Nightline" to its new, later slot. “Nightline” actually has more viewers than “Jimmy Kimmel Live,” but Mr. Kimmel's show generates more than twice the revenue because of its younger audience.

“The lessons are that credible, unbiased, national news is having an increasingly difficult time in reaching an audience large enough to be profitable,” says Richard Goedkoop, professor of communication at La Salle University in Philadelphia. 

Though "Nightline" will also get a new, prime time weekly show in prime time Friday, many media experts say the move harbingers the program's slow death.

“This is sad for ABC News, which will lose a time slot and the resulting advertising funding, and sad for those few who still watch 'Nightline,' " says John Goodman, a former senior producer at ABC and CBS News, who is now in public relations. “Nightline" is a casualty of “the constant changing entertainment alternatives, the dozens of cable-news programs that air during the day that often cover the same news stories, and TV executives who have little interest in offering time to the network news divisions.”

"Tonight" and "The Late Show" face problems of their own.

For its part, "The Tonight Show" has never recovered from NBC's decision in 2010 to move Leno to a 10 p.m. weeknight show. The show flopped, and Leno controversially returned to "Tonight" to replace his replacement, Conan O'Brien. "The Tonight Show" attracted more than 5 million viewers nightly before the move; now it has 3.3 million.

More broadly, though, Leno and Mr. Letterman appear to be losing their freshness. 

“Leno and Letterman's problems stem from the simple fact that their acts are getting old,” says Robert Thompson, founder of the Bleier Center for Television and Popular Culture at Syracuse University in New York. He says Letterman “totally revolutionized late-night in 1982, but after 30 years, he seems tired, and younger people have adopted and adapted his innovations. Leno, of course, is still working in the Carson tradition, partying like its 1979.”

Kimmel is less relevant than Mr. Stewart as a political comedian, “but his ability to incorporate online trends into an old-school network comedy show demonstrates moments of real brilliance," says Professor Thompson. "He features Internet trends and creates new ones of his own. He's also an excellent interviewer – in the modern idiom."

"To a lesser degree, Kimmel is now where Letterman was in the mid-1980s,” Thompson says. 

Jimmy Fallon, whose show follows "The Tonight Show" on NBC, may take Kimmel’s strengths even further. He regularly features a Twitter feature and keeps a laptop at the desk with him. With Leno’s contract set to expire in September 2013, speculation has already begun on whether NBC might bump Leno again, though NBC might feel chastened by the previous musical chairs fiasco.

To some, the recent moves point to a cheapening of late-night television.

"Kimmel’s show generates more advertising revenue than do the traditional network late-night shows, because it appeals to younger viewers. This shifts the political discourse somewhat: Kimmel, like Stewart and Colbert, treats politics as a joke. Younger viewers are turned off politics, preferring Facebook, iPods, and vodka," says Ben Agger, director of the Center for Theory at the University of Texas, Arlington. "One wonders whether anyone will be watching the networks in a decade, especially late at night when we aging baby boomers are in bed."

To others, though, the moves point to a new vibrancy in late night. 

Thompson suggests: “As far as civic relevance is concerned, late-night TV comedy is in a healthier state now than it's ever been before.”