If there is, were are damn lucky. However, Martin and ESPECIALLY Benedict are ridiculously busy, and their fame levels are shooting up quickly. They’ve both made it to the big screen in some very big films in some very big roles, and I don’t know if series four is doable. My guess is they will end it at series three, episode three. There will be no cliffhanger, we will just be left to assume that things go on as usual: Sherlock and John solving cases, Anderson lowering the IQ of all within a mile radius of him, Lestrade not giving a fuck, Mrs. Hudson being awesome, and tons and tons of subtext.