"Sherlock" season 4 is still a long way off as it was previously reported that the earliest the next season could premiere is in 2017. However, clues regarding season 4's plot have been littered by the showrunner and writers, and according to Cross Map, even the latest Victorian-era special episode gives a hint of what's to come.
According to the report, the year 1895 will play a big part in season 4's main story. This is the year that "The Abominable Bride" was set in but it is also the year that the original Arthur Conan Doyle stories were popular. It was the year Doyle published "The Final Problem," the story that killed Sherlock Holmes in his fight against Moriarty.
1895 was also teased in earlier seasons. The number was most prominently seen as the number of views on Watson's (Martin Freeman) blog right when he noticed that it was not increasing despite his best efforts to keep the blog updated with new case stories.
While the number may be a random Easter egg for "Sherlock Holmes" fans, it is now hinted as a major clue on what is to come. Fans speculate that this may be a referrence to stories published in 1895 and that any of these may be the basis for the story of season 4 while other fans speculate it will have something to tie in with Moriarty (Andrew Scott).
It was previously reported that season 4 will be darker and this may be a hint at a major character's death. Watson's wife, Mary (Amanda Abbington), dies in the original stories by Doyle and it is likely that the character will be killed off or at least seriously injured in season 4. There are speculations that Sherlock (Benedict Cumberbatch) himself may be facing serious harm.
This is only further implied by Freeman's comments when he spoke with Entertainment Weekly early last year, claiming that since she died in the books, it is likely she will die on the show, too.
