Earlier this year, co-creators Mark Gatiss and Steven Moffat revealed they had already outlined the next two series of the hit BBC detective drama. But, according to Martin, season four might not be the next time we see Sherlock and Dr Watson in action.
Martin Freeman has said that Sherlock might return as a one-off special
"Mark Gatiss may beat me up, but there is an idea for this one-off special that's such a good idea, and as I was listening to it I thought, 'We've just got to do this'," Martin told Alan Carr at the recording of this Friday's Chatty Man. "And I don't know when we are going to be able to do it, unfortunately.
"It's a fantastic, really mouth-watering idea. But I really don't know when we are going to get to do it."
Martin's assertion that the next instalment of Sherlock might be some way off won't surprise fans — traditionally there have been two years between series, in no small part because of Martin and Benedict Cumberbatch's increasingly busy schedules.
Benedict Cumberbatch and Martin Freeman as Sherlock Holmes and Dr. Watson
It's possible that the one-off episode Martin referred to is a Sherlock Christmas special. Mark Gatiss has made no secret of the fact that the Yuletide story The Blue Carbuncle is among his favourite of the Sherlock Holmes adventures.
Whether its in a one-off special or a new series, viewers will be hoping the next episode of Sherlock provides answers to the dramatic final scenes of season three, which saw Andrew Scott's Moriaty supposedly come back from the dead.