The state of the late: Will Leno, Stewart and O'Brien all change employers?

Later this month, David Letterman will begin his 16th year on CBS -- and the last in his long-running rivalry with Jay Leno on NBC.

For most of a decade, little has changed on the late-night TV landscape. Leno's ruled the roost ever since the mid-1990s. Letterman has battled shingles, heart problems and the turmoil of 9/11 in recent years, but that fight for ratings supremacy ended long ago.

Even ABC, which fired Bill Maher in 2001 and said so long to Ted Koppel three years ago, has been a bedrock of late thanks to the steady success of Jimmy Kimmel and a rebooted "Nightline."

That's all about to change, though.

At the end of next season Leno will hand the reins for "The Tonight Show" to Conan O'Brien, who in turn will relinquish "Late Night" to Jimmy Fallon. Leno agreed to this transition nearly four years ago. Since then, however, he has had Brett Favre-like resentments about being hustled into early retirement.

What will happen after O'Brien takes over is anyone's guess. Leno, it is rumored, is ready to sign with ABC, which would jettison "Nightline" in a heartbeat. Even Kimmel recognizes what a boost Leno would be to his own fortunes and is reportedly on board with having "Jimmy Kimmel Live" bumped a half hour later to make room for an hourlong Leno show.

At my website TVBarn.com, I've been carrying on a spirited discussion with readers who are absolutely convinced O'Brien will tank. "Yes, I will concede that Conan will enjoy increased ratings -- not for long, though," wrote one reader. "Just as Conan is settling in, BOOM, Jay Leno returns on another network! Conan will kiss it good-bye at that point."

"Just as Conan is settling in"? Actually, according to math I did based on interviews with NBC executives when I visited Los Angeles last month, O'Brien will have at least a 10-month head start on Leno. "The Tonight Show" will switch hosts on June 1, 2009. Leno's contract with NBC isn't even up until mid- to late autumn -- and only then will he even be allowed to talk with ABC.

After all the rigamorale of signing a deal, hiring a brand-new staff and crew (because why his current staff quit their permanent jobs at NBC) and getting a studio built, Leno won't be hitting the air again until spring of 2010 at the earliest.

Speaking of which, that's when Letterman's contract expires. Now, I don't want to say Dave's been phoning it in, but I hear he recently switched to the Sprint Unlimited plan. If he decides to call it a career when his current deal ends, Jon Stewart would be the odds-on favorite to take over "Late Show," if he wants it. Certainly the man who would follow him, Craig Ferguson, thinks he should: "Jon has earned the job," the clever Scotsman said in February.

However unlikely it seems, the prospect of Leno, Stewart and O'Brien all switching jobs is so tantalizing that many late-night watchers would like to see it happen.

But I'm not sure that any of that -- Letterman quitting, Leno jumping, O'Brien bombing -- will happen.

As I noted above, Conan O'Brien will have had plenty of time to settle in before Leno signs on. O'Brien is a better pairing with Fallon than Leno is with Kimmel. And here's another thing: Didn't ABC spend years trying to get the 60-something Koppel out the door? Why, then, would they want a 60-year-old comic in his place?

This is not the critic talking here; this is the guy who looks at Nielsen ratings. Leno's audience is big, and he enjoys the biggest viewership of the big networks among young viewers. Many of those younger viewers, however, also stay tuned for Conan. ABC would be paying Leno big bucks (the figure of $45 million salary has been put out there), and hoping he brings lots of people under the age of 40 with him. But he's just as likely to bring over lots of older viewers. And what about the people currently watching “Nightline”?

A college instructor who once worked for O'Brien as an intern has a unique perspective on the situation. He posted this comment to TV Barn: "Even while working on the show, I was among those predicting his cancellation; the poorly delivered jokes, the lack of chemistry with Andy, the conceptual comedy sketches that got few laughs, etc.

“Over a decade later, Conan not only survives, but to my students (with no memory of Carson, and only a fleeting idea of how great Letterman was in his heyday on NBC), he's the king of late night."

Note: A version of this piece appears in Sunday's Kansas City Star.