There is still a big question mark on when "Sherlock" Season 4 will begin production. The actors as well as the writers have mega-busy schedules and "Sherlock" is not the only show, or movie, on their minds. Thanks to the phenomenal success of "Sherlock," Benedict Cumberbatch and Martin Freeman have emerged as the most sought out actors both in the U.S. and UK. According to media reports, the main reason for the delay in production is the busy acting schedules of these two actors.

In one of the interviews, Martin Freeman had indicated that the original schedule to begin the shooting of "Sherlock" Season 4 was in autumn 2014. It seems the original plan could not turn into actual filming because of the non-availability of the cast.

"Conversations are still ongoing regarding Sherlock's return. Steven Moffat has already said that he has mapped out a fourth series, but it is always depending on cast availability," a source had said to Mirror Online in April.

Mark Gatiss and Moffat, co-creators of "Sherlock," have not only mapped out Season 4 of "Sherlock" but Season 5, as well. But, these two writers are also very-well aware that Cumberbatch and Freeman are currently the most in demand actors in Hollywood and Britain.

"Everyone is very keen to do more, but we have accidentally cast the two most successful actors in the world and schedules are tight," the creators had said after the telecast of Season 3 finale.

In a recent report, RadioTimes.com speculated that there is a possibility that "Sherlock" Season 4 will begin production in 2015 and the much-anticipated season will be telecast at the end of the year. "It will not be this year -- but 2015 is very much the hope and expectation," a source said to RadioTimes.com while speaking about the Season 4 production and telecast status.

At BAFTA's Awards, Gatiss said that they are close to agreeing on the production schedules for Season 4.

Despite what the sources tells, "Sherlock" Season 4 is unlikely to get a broadcast date before 2016. And seeing the signing spree of Cumberbatch and Freeman, it may not come as a surprise to anyone if the waiting period for the premiere episode of Season 4 gets longer.

Recently, it was reported that Cumberbatch will be doing voice-work in the movie "The Penguins of Madagascar." The actor will be taking-up the role of Classified, "a dashing-looking wolf with a serious set of eyebrows, in the next instalment of the Madagascar movies, according to The Guardian.

Meanwhile, Freeman is currently starring in FX's anthology series "Fargo."