Thought this was deader than Elvis. Maybe not. Hopefully lots of estrogen infused REEEING when Cumberbatch either flat out says "fuck no" or demands so much money it amounts to the same thing. If I did Tumblr I'd check out how they're taking this, but, alas I do not.
Sherlock: “I sort of assume we’ll come back”, says Moffat
If you'll allow me to Sperglock for a minute, pretty much the whole crew sees this as a passion project. That's why everyone's family wound up in seasons 3 and 4 (B.C.'s parents, Amanda Abbington, etc.). So everyone's said at some point, "Oh, it'll be fun if we can do this every few years until we're old." BUT with Cumberbatch and Freeman both being owned by Marvel now, it was pretty clear that it was time to put a bookend on the series for now. They left a lot of stories untouched, so it's not impossible. But it's possible that the fandom's sheer size and insanity ruined things for everyone.
(Though I will say, Cumberbatch is good about coming back to the things that shaped him. He was on the radio show "Cabin Pressure" pre-Sherlock, and he came back for the final episode even after his meteoric rise in popularity.