Sometimes being an incredible superteam is good for some things. Like deciding that your television show will get another season. Which is what Benedict Cumberbatch and Martin Freeman basically did for Sherlock.
According to Steven Moffat, Cumberbatch and Freeman announced that Series 4 was happening before he or the BBC knew. “They signed themselves up. They both announced that they were carrying on—so that’s good.” Then he and Gatiss had to inform the BBC that Benedict and Martin had commissioned the new series for them...
Moffat was quick to point out that “The BBC can do what they like. They're massively powerful, don't provoke them! But I assume that unless we've really screwed up [the upcoming series of] Sherlock—which we haven't—it's a big success and it will carry on, so long as Benedict and Martin want to do it.”
And Cumberbatch is on record saying that he will play the part of the Great Detective forever. So we can look forward to watching him go gray in the role, with a little luck and Freeman by his side.