Martin Freeman and Benedict Cumberbatch love doing it;
Mark Gatiss and Steven Moffat love doing it;
Gatiss is already writing The Return episode;
Despite being massive trolls about how Sherlock survived, I think they really, really, REALLY want to show us how he did it so that we can praise their cleverness forevermore;
They want to finish Series 3 on an EVEN BIGGER CLIFFHANGER, they would never miss the opportunity.