Robert J. Thompson, who runs the Bleier Center for Television and Popular Culture at Syracuse University, sees Kimmel's time switch as era-defining.
"If he can compete in that period, I think that could completely change and finally solidify the idea that while 'Tonight Show' has got this long legacy and people like Letterman and Conan so much revere it, the fact is the 'Tonight Show' might not any longer be the Holy Grail of television."
He added: "I'm not even sure it's the Holy Grail now, to be honest."
Certainly "Tonight" isn't throwing off the cash it used to. But gold mines have grown scarce in late-night TV overall, as competition and lowered ratings take their toll.
NBC's "Tonight" delivered a reported $100 million to NBC's bottom line during the show's 1990s heyday, but TV veterans say the show is barely profitable now. And most competitors are in similar straits.
Last summer, In mid-2012 NBC forced layoffs at "Tonight" for only the second time in the show's nearly 60-year history. NBC executives declined to comment on reports that they are looking to jettison Leno as early as 2014 and replace him with Jimmy Fallon, currently the host of NBC's 12:35 a.m. show.
Despite the recent history, ABC's brass is optimistic about Kimmel's prospects.
"We think it's time," said Paul Lee, president of ABC Entertainment Group, in an interview. "We think we can build ourselves a big entertainment asset in late night."
Regardless of how that plays out, the head-to-head-to head-competition offers a chance for some backstage drama as well.
Relations between Letterman and Leno have been frosty ever since NBC picked Leno to succeed Carson, leading Letterman to bolt for CBS. But Kimmel is a hardcore fan of Letterman, an elder figure who has returned the kind words in interviews. Letterman appeared as a guest on Kimmel's show late last year when it was broadcast from the Brooklyn Academy of Music for a week.
"For David Letterman's second-year anniversary on NBC, I drew pictures of him on buttons for everyone that came to the anniversary party I had at my house," Kimmel recently enthused to reporters.
But Kimmel has extended no such good will toward Leno, who has become something of a villain in TV circles after he returned to "Tonight" following an ill-fated prime time show a few seasons back. Leno's return meant the end of Conan O'Brien's turn as host – a tenure that lasted less than a year.
"Jay Leno is not going to be able to stay on television forever," Kimmel said. "But, you know, with that said, never count Jay out. He's like Jason in 'Friday the 13th.' He seems to pop up just when you think he's dead. He comes back to life and he's got a hatchet."
That's not the plan Kimmel has for the rest of his career. "I'm not going to be one of those guys that they have to drag off the stage," he told reporters. "I mean, I look at it now and I think, 'You know, if we were lucky enough to be able to do another 10 years, I would be very happy with that.'"
Times staff writer Meredith Blake contributed to this report.