'Sherlock' season 4 spoilers, rumors: Upcoming season to be the last

BBC's "Sherlock" has become such a pop-culture phenomenon, and it is responsible for making actor Benedict Cumberbatch a full-fledged star. Rumors are going around online that this season could very much be the last of the series, and speculations are guessing that there will be an appearance from a third Holmes brother.

According to Christian Daily, the Sherlock panel at the San Diego Comic-Con teased the upcoming season with the words "Thatcher. Smith. Sherrinford." Fans have been going crazy online, trying to find out what the words mean, and some have guessed that it could allude to a third Holmes sibling that has been hinted at in the past season.

The third season also hinted at the possible return of Andrew Scott's James Moriarty. In possibly one of the series' most memorable episodes, Moriarty shoots himself in front of Sherlock in an attempt to force Sherlock to kill himself (which he did, kind of). How Moriarty managed to fool Sherlock that he had killed himself is a mystery, but it is possible that he still is dead, and all of the events are just something Moriarty had planned beforehand (reminiscent of "Saw's" Jigsaw).

This upcoming season will have Toby Jones playing the villain Culverton Smith, a character that appeared prominently in the Sherlock Holmes story "The Adventure of the Dying Detective." It is interesting to note that Jones has played a villain in the Marvel Cinematic Universe, and "Sherlock's" two leads, Cumberbatch and Freeman, have also landed roles in the MCU (the former helming his own movie as Dr. Stephen Strange in "Doctor Strange").

In an interview with Collider, Cumberbatch may have hinted that season four "may be it" for the series, and with the busy schedule that the lead actors have been having, maybe it's high time Sherlock is finally put to rest.

The next season of "Sherlock" is expected to hit next year.