|You will find out in the far future how I survived my fall.|
If it is driving you crazy trying to figure out how Sherlock survives the fall then it will drive you insane to find out that it will be quite a bit longer than you expected for Sherlock to return. According to Beryl Vertue, who is one of the Executive Producers on the show, that "Filming will start in early 2013." So that could mean that Sherlock might not return to our TV screens until late 2013 or even worse early 2014. This is not all that surprising considering the how busy the two stars are as one is filming the Hobbit and the other is filming Star Trek. Bummer but at least there is still a third series to look forward to.
Source - BBC Early 2013 Filming For Sherlock