“Sherlock” Season 4 premieres Sunday, but fans are still wondering if this could be the last season premiere the British series airs. Executive producer Steven Moffat doesn’t have a clear answer on the fate of PBS’ hit drama.

“We don’t actually know,” Moffat explained to Newsweek. “We thought [Season] 3 would be the last one.”

Stars Benedict Cumberbatch and Martin Freeman are more popular than ever, but many are worried that their thriving careers won’t help the show. Instead, they might be too busy with huge franchises to return to the TV show. However, Moffat noted that it’s just a matter of scheduling. “It’s difficult. It’s not impossible because we don’t need that much time from anyone. But it’s finding the right gap,” he added.

Moffat has been on rumor patrol since at least October, when Cumberbatch, who plays Sherlock Holmes, was quoted in British GQ as calling “Sherlock” Season 4 “the end of an era.”

“That’s not what Benedict said,” Moffat told Entertainment Weekly. “That’s what someone edited his words into the meaning. … We don’t know. We haven’t sat down with the intent to anything yet. But we’re always aware that it could be over. But the fact is Benedict did not say that.”

However, while Moffat has been clear that the future is unknown, his stars have sounded a bit more ominous when talking about the future of “Sherlock.” Freeman, who plays John Watson, visited Jim Norton and Sam Roberts’ SiriusXM radio show and seemed to tease that the end is near.

“This last series did have a feeling of, I don’t know whether it has a finality to it, but it certainly had a feeling of a pause,” Freeman noted. “And I am never ever afraid of things ending. I mean I am not looking forward to life ending or love ending, but things that we make, should end.”

Cumberbatch noted a similar feeling. “This new series goes to a place where it will be hard to follow on immediately,” he told Weekend Magazine. “We never say never on the show, but in the immediate future we all have things we want to crack on with, and we’ve made something very complete as it is.”

Should the show be canceled, it would likely be a creative decision. As of last year’s New Year’s Day special, the show was doing very well in ratings. Over 11 million U.K. viewers watched the special on BBC One, and Season 4 is expected to maintain good numbers. However, it seems fans won’t know if it’s the final season for quite a while.

“Sherlock” Season 4 premieres Sunday at 9 p.m. EST on PBS.