How many seasons?

There are only 2 seasons each of them having only 3 episodes of 90 min.
It was confirmed によって Steven Moffat that in 2013 there's gonna be a third season.Right now Benedict Cumberbatch(sherlock) and Martin Freeman(john watson)are busy with other projects like "Star Trek" または "The Hobbit"
I think it's early to talk about a fourth season:)

They promised us at least 4 seasons. あなた can check out tumblr, you'll see I'm right. Peeps are freaking out right now...

Personally, I think there will be 3 seasons. It's the best option. Everywhere they have added the 'threes' - 3 episodes each season, every episode 90 min long (= 3*30)... And 3 seasons. It would be just perfect! I hope the third season will be the last.

There will be a season 3, it's been confirmed.


link

''Co-creator Steven Moffat promises that it won’t be “too long” before you’ll be seeing Sherlock (Benedict Cumberbatch) and Watson (Martin Freeman) back at 221B Baker 通り, ストリート – just don’t expect it to be all that soon.''

But apparently there won't be any other seasons.

73 and the last season I will watch when I will be 99 years and when at last I will see Sherlock&John `s キッス I will die quietly :D
hehehe :)))))

There'll be at least a fourth season. It's been confirmed.