Now that the show is under production, the fans are already wondering who the villain will be. The rumor is rife that this new antagonist on the show will somehow be connected to James Moriarty (Andrew Scott), who is Sherlock's arch-nemesis and presumably dead.
The fans also speculate that in one of the previous seasons, Sherlock says, "It's never twins, Watson!" The show enthusiasts now wonder if season 4 will indeed throw twins in Sherlock's path. Others also hint that the twins might be Moriarty and Sherlock has been dealing with several Moriartys, without even knowing about it. There are also reports that Irene Adler from season 1 will reappear again in this season as Sherlock's love interest.
Meanwhile, other reports indicate that Toby Jones will play the character of Culverton Smith, a villain from Sir Arthur Conan Doyle's "The Adventure of the Dying Detective." This character's objective is spread deadly infection, which Sherlock somehow dodges, pretending to be too sick to investigate. However, since Steven Moffat is known to add some of his modern touches to the storyline, it is possible that it will turn out to be different from the book.
While there is no news about the official release date of the show, word is that Sherlock will most likely be out by mid-2017. Fans can also expect to see a Christmas special episode, if the producer's schedule permits.