'Sherlock' season 4 spoilers, news: Benedict Cumberbatch confirms end of series? 'Creepiest' villain introduced in upcoming season

Production is underway for "Sherlock" season 4, and it's expected to drop in early 2017 on BBC. However, its airing might just be bittersweet for loyal viewers who have followed the detective drama since its maiden season.

Collider caught up with Benedict Cumberbatch, who plays the titular character, at the San Diego Comic-Con in July, and he was asked about the fate of the BBC drama.

"We'll see how this series lands. It's been great fun to come back and do it. How it will continue in the future, who knows?" he said. "It's not just about what any of us want. It's about what's actually right for the show, to be honest, and that has to be judged very carefully. ... It's a painful thing to say, but maybe series four is it. Who knows?"

The Oscar-winning actor did say he hopes "Sherlock" would see more seasons, as he enjoys doing it. However, he was quick to add that both cast and showrunners are "all being stretched in different directions."

Cumberbatch's words echo those of Steven Moffat, the show's executive producer, who said Cumberbatch and Martin Freeman, who plays Watson, are highly in demand these days. In fact, Moffat said the actors are only doing the fourth season "out of loyalty to fans."

Meanwhile, Toby Jones' still unnamed character is touted to be "Sherlock's" creepiest villain to date. In the interview with Collider, Moffat said Jones' character will be "the darkest villain" the show has ever had.

"This guy is the purest evil. Sherlock is actually appalled by him. He's the most evil villain we've had. I don't think that when you see it, you will disagree. He's horrific," he said.

Moffat and co-executive producer Mark Gatiss even pointed out that Jones is not just creepy on the outside. A deep evil runs in him that "sends chills" down Sherlock's spine.

Excited to find out just how sinister Toby Jones' character would be? "Sherlock" season 4 is expected to drop in early 2017 on BBC.