A fifth season of "Sherlock" is looking highly unlikely. One of the show's writers, Mark Gatiss, said that they are finding it hard to push Season 5 due to the lead stars' tight schedules.

Season 4 ended on Jan. 15 and though fans would very much like "Sherlock" to go on beyond Season 5, Gatiss admitted that they "don't know if there will be any more" because of Benedict Cumberbatch and Martin Freeman's other commitments, The Sun reported. The former is currently busy filming Marvel's "Avengers: Infinity War," though there are reports that even the superhero movie can't manage to pin down the actor - at least for now.

According to Screen Rant, a stand-in is being used for Cumberbatch's scenes in "Avengers: Infinity War" because the actor is currently held up by the filming schedule of the movie "The Current War." Once filming in the latter is done, Cumberbatch will reshoot all of his Doctor Strange scenes where his face is seen.

Freeman, meanwhile, is also a part of another Marvel movie, "Black Panther," as Everett Ross. In addition, the actor is involved in the film adaptation of the West End play, "Ghost Stories."

Despite the improbability of Season 5, Gatiss is happy about where they left "Sherlock" Season 4. He described their last filming day for the series as "odd" and ending "with a whimper."

Showrunner Steven Moffat said that the ratings for the series "were extremely good," Den of Geek reported. He acknowledged the rewards and acclaim that the phenomenal show got over the years, but "not doing it again would be fine" and the crew is okay with Season 4 as their last run.

Moffat, however, thinks that BBC would like another season but that depends on the lead stars' schedules. Every season of "Sherlock" may only have three episodes each, but making them is no small matter. Moffat likens each episode to a film and for good reason; one episode runs for more than an hour.

A rumor, however, has claimed that one of the reasons why "Sherlock" Season 5 will not happen is because of Cumberbatch and Freeman's "frosty friendship." The Sun cited a source saying that the two "aren't mates and they don't spend time together" outside of the show.

The actors act "professional and very polite" with each other but the warmth of friendship is missing even after working closely together for six years. The news outlet added that Cumberbatch and Freeman have no big desire to reprise their roles as Sherlock Holmes and Dr. John Watson (who are thick as thieves in the source material) for Season 5.