A.V. Club reports that Benedict Cumberbatch suspects series 4 might the end of Sherlock. This notion is contrary to previous reports that Cumberbatch has signed for series 5 (in conjunction with series 4, reported in early 2014) and that Steven Moffat and Mark Gatiss have "plotted" series 5.
Honestly, I wouldn't be surprised considering Cumberbatch and Martin Freeman have such busy schedules, especially for Cumberbatch as he head dives into the Marvel Cinematic Universe.It feels like the end of an era, to be honest. It goes to a place where it will be pretty hard to follow on immediately. We never say never on the show. I’d love to revisit it, I’d love to keep revisiting it, I stand by that, but in the immediate future we all have things that we want to crack on with and we’ve made something very complete as it is, so I think we’ll just wait and see. The idea of never playing him again is really galling.