There's more than one reason John Oliver's imminent HBO deal is inconvenient news for The Daily Show. Here's the obvious one: Jon Stewart has lost his trusty (and well-liked!) sidekick. Here's the less obvious (but perhaps more troubling) one: Jon Stewart has lost his eventual successor—or so goes the conventional wisdom. Where does that leave The Daily Show now?

But let's back up. Oliver, a British comedian, has been with The Daily Show since 2006, but he didn't get his turn in the hot seat until this past summer, when he spent a whopping eight weeks filling the elder host's shoes while Stewart jetted off to make his directorial debut. And he did a good job! He made for a likable, frequently hilarious host, mocking the bejesus out of Anthony "Carlos Danger!" Weiner (an old friend of Stewart's, making Oliver a well-timed stand-in) and leading the helm for memorable sketches like stop-and-frisking Wall Street. Too good a job, really, considering HBO just swooped in and snatched him from Comedy Central's clutches.

But even before Oliver finished up his guest residency, critics and viewers were speculating that it was really more of an eight-week audition. Stewart's been with The Daily Show for 14 years now, and he can't stick around forever, can he? Everyone gets restless, and who better to take over than the show veteran who already took over for two months with almost unanimously heralded success? Entertainment Weekly's Hillary Busis speculated along such lines, writing that the Great John Oliver Experiment proved The Daily Show with Jon Stewart can, in fact, exist without Jon Stewart. "If there’s any justice," wrote Busis, "Oliver won’t have to stay a second stringer for long." Vulture's Jesse David Fox similarly declared back in August that "we can now consider John Oliver The Daily Show's heir apparent." Now what?

"Right now I don't think they have any clear sense of what they will do if Jon [Stewart] leaves when his contract is up in 2015," Fox told The Wire this week. "You look at the people on the showI think there's no next in line."

But, Fox added, the show evolves quickly, and personalities come and go.

"As always with the show, they only have room for really a star or two [star] correspondents. So it's very possible that because John [Oliver] is leaving, Al Madrigal will get more comfortable with the show and he might make sense. Or Aasif Mandvi will kind of assert himself," Fox speculated. "If [Stewart] were to take two months off right now I don't know who'd do it, but we're assuming he'll wait until next summer to take time off."

The Guardian's Amanda Holpuch, who called Oliver the "heir-apparent" back in June, has a different idea. 

"While Oliver was primed to take over the host seat because of his excellent work this summer, I think The Daily Show has another obvious heir to the throne: correspondent Jessica Williams," Holpuch suggested in an email. "She's hilarious, a woman, and youngshe started at the show last year when she was 22 and carries segments with the ease of correspondents nearly twice her age."

None of which is to say Stewart's definitively on his way out, but his contract is up in the middle of 2015, and what if he's developed a real taste for movie-making? What if fatigue really has set in? As always, speculation abounds.

"I interviewed [Stephen Colbert] last week and I saw him speak and he was like, 'This is the greatest job I've ever had. I would never want any different show,'" Fox recalled. "I feel like I haven't heard Jon Stewart say that sort of thing any time recently."

Hence, the summer's experiment. Only problem is, Oliver aced his audition a little too well, and now Stewart's back where he started.