Mark Gattis - the shows co-creator, writer and actor - (Mycroft Holmes) announced that they already finished filming "Sherlock" Season 4, with its release scheduled in January 2017 - three years after the last episode of Season 3 was shown.
He described the upcoming season as "big chewy stuff, meaty" and "the best one" that they have done so far. By his words, "life changing things can happen".
Sherlock's archenemy, Moriarty, is presumed to return. However, how his comeback might be is yet to be known since he has killed himself in Season 2.
There is another villain, to be played by Toby Jones, from Arthur Conan Doyle's novel that will make a debut in Season 4. Can this villain be Culverton Smith, the worst villain of the show yet?
It looks like the years of waiting for Season 4 to premiere will be worth it. But unfortunately, Season 4 can also be the show's season finale
Steven Moffat, creator of the show, said that it is possible that Sherlock will end next season because of the availability of the main actors, Benedict Cumberbatch (Sherlock Holmes) and Martin Freeman (John Watson).
BBC's "Sherlock" Season 3's last episode was shown in January 2014. Though fans are partly restrained by the special one episode of show entitled "The Abominable Bride" released in January 2016.