BBC 'Sherlock' Season 4 Air Date & Premiere: Steven Moffat Promises to Top Previous Seasons, Possible Spin-Off in the Works

"Sherlock," the critically-acclaimed BBC TV series, is slowly headed toward its Season 4 premiere. Nonetheless, show-runners have adopted the philosophy, "go big or go home" for the upcoming Season 4.

Series creators and writers Mark Gatiss and Steven Moffat have announced that they've already begun penning the plots for the fourth and fifth seasons, needing only scheduling conflicts to be resolved before they're able to get the show on the road.

The rumor mill has been busily churning, and multiple sources have offered that archnemesis Jim Moriarty (played by Andrew Scott) to protagonist Sherlock Holmes (played by Benedict Cumberbatch) may return from the grave, foreshadowed in the sensational finale of season 3. Cumberbatch also hinted at the return of the villain, vaguely stating, "to forget in order to rediscover it again a little bit."

"It's going to be full of surprises for you, and for us and for everybody. I think we just know to expect the unexpected now," said Martin Freeman, who portrays Dr. John Watson. "What has been explained to me and Ben [Cumberbatch] and Amanda Abbington -- my missus who plays Mary -- has been very exciting." Freeman also added that there could be a spin-off of the popular TV series.

"We practically reduced our cast to tears by telling them the plan. Honestly, Mark [Gatiss] and myself are so excited with what we've got coming up, probably more excited than we've ever been about Sherlock. ... Honestly I think we can [top the last season]," Moffat told The Hollywood Reporter.

Moffat's assertions prior to season 3 contradict the possibility that Moriarty will returning. As he's pointedly stated, Moriarty shot himself in the head, therefore it's "impossible for him to be alive." Nevertheless, Moffat has guaranteed hungry fans that they will once again witness much-loved ... and breathing characters continue games of cat and mouse with villains on the streets of London.

"Sherlock" Season 4 was meant to begin filming in January 2015, however two of the series' lead actors have other filming obligations. While the official air date has yet to be released, fans can expect that the series will begin filming in early 2015 and won't premiere until early 2016, with no specified dates. But, the show-runners have planned a Christmas special for December 2014, which will be based on the mystery "The Adventure of the Blue Carbuncle."

"We're working on it. We're working on dates," producer Sue Vertue told Radio Times. Co- producer Steven Moffat added, "We'll get them made as quickly as we can."

When the series does premiere in 2016, fans should also expect new cast members, one of them being the offspring of Watson and Mary Morstan. Also, actor Tom Hiddleston may be cast to play Sherrinford Holmes, Sherlock's hypothetical older brother. And, viewer may see more of more of Molly Hooper (Louise Brealey), Sherlock's friendzoned lab assistant.