It is on Netflix streaming, at least the first two seasons.
We may not get the third season until 2014.
"Fans of the BBC’s runaway hit Sherlock (a modernization of author Sir Arthur Conan Doyle’s Sherlock Holmes franchise) have been eagerly anticipating a third season since the cliff-hanger ending to the season two finale, “The Reichenbach Fall”. Co-creator Steven Moffat dosed that fire with more fuel a few months ago, when he announced a three-word tease hinting at which stories from Doyle’s source material are going to serve as the basis for each of the season’s three 90-minute episodes.
Sherlock Season 3′s planned premiere date changed from ‘When We’re Ready’ to Fall 2013, after Moffat dropped that juicy tidbit. Unfortunately, the latest reports indicate that date has been moved back due to scheduling issues – namely, those resulting from the newfound popularity of the show’s stars, Benedict Cumberbatch and Martin Freeman.
Now, any Sherlock fan worth their salt knows that the show/mini-series’ principal players (Moffat, Cumberbatch, Freeman) are very busy men. Moffat is currently serving as the showrunner for Doctor Who, which Sherlock co-creator Mark Gatiss writes for (in addition to making occasional onscreen appearance). Not to mention, it wasn’t that long ago that Cumberbatch wrapped his still-mysterious villain role in Star Trek Into Darkness and shot a supporting role in Steven McQueen’s true-story slavery drama Twelve Years a Slave; similarly, Freeman finished the first chunk of principal photography on Peter Jackson’s Hobbit trilogy this summer". http://screenrant.com/sherlock-seaso...-date-delayed/