The writer insisted that Moriarty (Andrew Scott) is unlikely to return following his apparent death, reports Radio Times.
"We need to find new villains, we need to find new ideas, otherwise the show doesn't keep growing," said Moffat.
"Moriarty's a one-shot deal in the original [books]. I don't want [Sherlock] to turn into a show that's about one villain and one hero. Moriarty was great because he was a surprise. Every time you bring him back he won't be as big a surprise."
Moffat hinted that the third series, which was confirmed in January, will introduce "other great villains" from Arthur Conan Doyle's stories.
"We have to keep the show growing otherwise it won't surprise you," he suggested. "Once you get the measure of it you'll just get critical - if we keep surprising you and keeping you off balance, you won't."
No air date has been announced for the third series of Sherlock, though executive producer Sue Vertue has claimed that the detective drama is unlikely to return before 2013.
eh idrc about him (sorry sis hypermuseic9)
less Moffat, more Godtiss, better-written Molly (coz Louise is lovely),