Production of "Sherlock" season 4 has been pushed to spring 2016, and fans will possibly have to wait till early 2017 or late 2016 to see what's in store for Sherlock now that Moriarty could be alive.

There is still no premiere date, but fans can expect a season that is both dark as well as funny, co-creator Steven Moffat revealed in an earlier interview. He also noted that the upcoming season will be very different from all its previous seasons.

"The first series was all about the beginning of their friendship. Second about the formative stages, the love and fear and loss and all that. The third was good days, me and my pal and my pal's wife. Those are golden days," Moffat told Entertainment Weekly a few months ago. "The missing element in a lot of Sherlock Holmes adaptations is allowing it to be funny. There's a lot of humor in Sherlock Holmes, and it's ignored in a lot of adaptations."

Besides being funny, the fourth season will also be about consequences, making it dark.

"[Season 4] is going to be… I suppose you'd say… consequences. It's consequences. Chickens come to roost. It's dark in some ways—obviously it's great fun and a Sherlock Holmes romp and all that—but there's a sense of… things… coming back to bite you. It's not a safe, sensible way to live. It's hilarious and exhilarating some days, but some days it's going to be bloody frightening," Moffat revealed.

Meanwhile, the one-off Christmas special, which is set in the Victorian era, is expected to solve the mystery of Jim Moriarty's message that was aired in the season 3 finale.

The final episode of season 3 entitled "The Last Vow" ended with Moriarty suddenly reappearing on television with the message, "Did you miss me?". It is still unknown whether the arch-villain is really alive or simply terrorising Sherlock with a previously recorded video.