Now that NBC has pulled the trigger, gunning down its top-rated late-night host to replace him with a younger and more cost-efficient model, you have to wonder: Is David Letterman next?

Like Leno, the long-time CBS Late Show host’s contract expires in 2014. And unlike the Tonight host, Letterman is older (65 to Leno’s 62) and lower rated (averaging a 0.7 in the adults 18-49 demographic to Leno’s 0.8). Conventional industry wisdom says there is a new late-night race to claim the next generation of young viewers. The starting pistol was fired by ABC moving Jimmy Kimmel Live to 11:30 p.m., and now NBC is making its play by shifting the 38-year-old Fallon into the Tonight seat.

CBS has long been remarkably calm amid other networks fretting over their late-night lineup. NBC has, in the words of Time’s James Poniewozik, “a neurosis around The Tonight Show … so afraid of losing its dominance, so bent on controlling everything and heading off any potential competitor, that it’s driven to overwrought 3-D chess moves that bring about the very disasters they’re meant to avoid.” While CBS has ambled along, seemingly content with having a solid No. 2 show, its insiders all amused by NBC struggling to overthrow its own popular host.

You could argue renewing Letterman for another round makes more sense than joining ABC and NBC in the next-gen scramble. There’s a good chance that all CBS needs to do to have the top-rated late-night show is wait. We’ve seen when Kimmel and, briefly, Conan O’Brien, were moved from 12:30 p.m. to an earlier slot, they enjoy a significant gain in viewership — Conan climbed 25 percent; Kimmel jumped 40 percent. But Fallon, who currently averages a 0.5 rating in the demo, would need to jump 60 percent to match Leno’s current number and beat Letterman. That’s not very likely. “In the short run, this is going to stack up pretty well for Dave,” says one late-night insider. “You have the two other guys who will have to slug it out for the younger audience, while Dave can greet Leno’s viewers with open arms.”

CBS Corp. chief Les Moonves has previously said Letterman can choose his own retirement date, and Letterman recently made it clear it’s up to Moonves. “He and I have an agreement,” Letterman told Oprah Winfrey in January. “When he wants me to go all he needs to do is call and say, ‘You know Dave, it’s time to go,’ and I’ll go. I’ll miss doing what I’m doing. But I won’t feel like I’ve left anything on the table. When it’s time to go, somebody else tell me. Because I don’t know when it’s time to go.” You can bet that whatever happens, when Letterman retires it will at least appear to be the late-night host’s choice (there will be none of this PR messiness of “categorical” denials and on-air sniping that have made headlines during NBC’s turnover).

For whatever it’s worth at this point, from poking around the Letterman camp and CBS, we’re not hearing of any desire to make a switch. One thing about Moonves’ strategy is that he has succeeded in prime-time by embracing older-skewing programming concepts — like crime shows and multi-camera sitcoms — rather than chasing younger viewers with the latest programming trends (CBS briefly had an experimental phase a few years ago, but nowadays the network would never have never greenlit Fox’s Terra Nova or NBC’s Smash). Slow and steady often wins the race for CBS.

If CBS decided to make a change, there are a few possible candidates. Comedy Central’s Stephen Colbert (48) is frequently mentioned. He appeals to relatively young viewers and has an easy-on-the-eyes old-time TV broadcaster’s good looks. In fact, by one measurement The Colbert Report just beat The Tonight Show for a full quarter among adults 18-49 for the first time, though Comedy Central uses a different ratings metric (broadcast traditionally includes repeats in their late-night rankings). “They’re all fighting for third place now,” brags Comedy Central’s ratings release issued this morning. Colbert’s appeal is largely untested outside his arch-conservative character, however.

Another possibility is Colbert’s late-night companion Jon Stewart (50), whose Daily Show has higher ratings than Colbert or Tonight. Stewart is a pretty big turn-off to conservatives, however, which is not an easily dismissible factor when discussing a late-night hosting role on a major broadcast network like CBS. (Letterman is a liberal too, but didn’t have years of political monologues bashing Republicans in the public consciousness when he took the job).

Also, Stewart is so perfectly suited for his Daily Show pulpit that it’s hard to imagine him wanting a platform as pedestrian and old-media as the Late Show. Yet with Stewart taking his eye-brow raising 12-week leave of absence from The Daily Show this summer, which will give John Oliver a turn in the driver’s seat, some are wondering if the Stewart is readying himself for something new.

The man nobody seems to mention is the most obvious heir on CBS’ schedule, Late Late Show host Craig Ferguson, and the numbers explain why. CBS is unlikely to replace Letterman with a host who has a track record of losing to Fallon at 12:35.

Keep in mind, some of these calculations could shift if one other long-shot thing happens: Fox hires Leno.