Don't be alarmed, but there's a possibility that 'Sherlock' won't be on our screens for much longer according to the show's executive producer Steven Moffat. Apparently, it hangs on the schedule of stars Benedict Cumberbatch and Martin Freeman - and the movie offers they're getting are only getting bigger.

'Sherlock'Will 'Sherlock' series 4 be the last?

Moffat has even gone so far as to say the next series - set to air next year - could be the last if the actors contine to be as successful as they already are in the film industry. However, he also claims there's a chance that, even if it did get cancelled, there's no reason it won't be able to return in the future.

Since 'Sherlock' began, Cumberbatch and Freeman have seen their acting careers skyrocket. While the former has gone on to star in the likes of 'Tinker Tailor Soldier Spy', 'Star Trek Into Darkness' and 'The Imitation Game', with his first Marvel role coming up as the titular 'Doctor Strange', Freeman had a leading role in the three-part film series of 'The Hobbit', appeared in 'Captain America: Civil War' and led season one of crime mini-series 'Fargo'.

They're two impressive resumes at a glance, so it's no wonder Moffat doesn't want to keep his hopes up too much about the future of 'Sherlock'. 'I don't know how long we can keep it going', he confessed to the Telegraph. 'I'm personally willing but I'm hardly the main draw. I would be moderately surprised if this was the last time we ever made this show. But it absolutely could be.'

He elaborated that there isn't a financial attraction for the actors anymore, given the extent of the blockbusters they have been involved with, but admitted that they love to get involved as much as he does. 'We do have two film stars in the programme', he continued. 'They haven't needed to do these jobs for a very long time. They're coming back because they want to. I'm amazed that we've got this far. I thought that once they had become extremely successful, we would only get to do one more series. There's never going to come a time when we do a longer run, because this is what the series has become. It's an occasional treat where you get three movies. It's how it works.'

More: Toby Jones to star in the next series of 'Sherlock'

The last episode of 'Sherlock' was the New Year's Day special 'The Abominable Bride', an episode which has landed it six Primetime Emmy nominations this year. It got over 12 million BBC viewers and was the biggest overseas export for the company in a year. Details regarding 2017's fourth series remains under wraps, but we do know that Toby Jones has signed on to play the next big villain and that there won't be any direct reference to an original Arthur Conan Doyle story.