The third trio of Sherlock episodes were due to start filming in January 2013, for a potential release in late-summer. This has now been pushed back to March 2013, accommodating Benedict Cumberbatch and Martin Freeman's hectic work schedules, meaning a late-autumn or Christmas release is more likely. That's practically a year away, so the gap between series 2 and 3 will be almost two years!
Let's hope the explanation for Sherlock Holmes cheating death is still something audiences care about, or feel was worth such a very long wait...
However, to be more upbeat about all this, you often wait a similar amount of time for resolutions to a movie. And at least we're still getting a third series, given Cumberbatch's sudden popularity and work schedule. It's primarily his commitment to the character that's keeping this show going—not unlike the similar loyalty of co-creator Steven Moffat (who's got a very busy year ahead masterminding Doctor Who's 50th anniversary celebration). And let's not forget regular director Paul McGuigan, who has his own film projects in the pipeline just now.
It's disappointing news for fans, but Sherlock's only really slipping back by a few months or so. There's even a chance the production will make an intensive effort in post-production to try and shrink the broadcast delay, who knows. But, the more I think about it, the more it feels like series 3 could be the last... unless Freeman wrapping on The Hobbit trilogy and Moffat potentially stepping aside as Who showrunner makes Sherlock a far easier logistical feat in 2014.