The British star, 38, will return as the beloved sleuth in a Christmas special next year, with a three-part series to follow in 2016.
CLICK ON PHOTOS TO ENLARGE
Benedict Cumberbatch has said the new series of Sherlock will be 'phenomenal'
"I can't give any plot away… but their pitch for the Christmas special and the series beyond that is just phenomenal," Benedict told Empire.
"We've never seen (Sherlock) being really pressed yet, so that will be interesting."
The star also admitted that his love for the character is so strong that he could happily play Sherlock as a pensioner.
"As long as the ideas are still there and the audience still wants it, and as long as Martin (Freeman) and I are not too infirm that we can no longer remember lines and shuffle around the set, I'd love to do it into old age, I really would."
Benedict Cumberbatch and Martin Freeman as Sherlock and Watson
Meanwhile, Sherlock creators Mark Gatiss and Steven Moffat have already said they have "devastating" plans for the fourth series.
Speaking at the Emmys in August, the pair said, "We've practically reduced our cast to tears telling them the plan.
"We're probably more excited than we've ever been about Sherlock. We've got a very, very good set of ideas."