Vertue, who is speaking at the Nations and Regions Media conference in Salford today, told Ariel that it was too early to confirm transmission times for the next series.
But it means fans have a long wait to learn how the detective faked his death at the end of the second series.
The drama, which has been a massive hit with around 10 million viewers, was co-created by Vertue's son-in-law Steven Moffat and is produced by his wife Sue Vertue for Hartswood Films and BBC Wales.
Filmed in Cardiff and London, it has also sold to 200 territories.
Leading actors Benedict Cumberbatch and Martin Freeman are currently filming abroad on the next Star Trek movie and The Hobbit respectively.
Well this kinda sucks. Going by the fact that they started filming the second series in May 2011 and it took seven months for it to air on the BBC that means August 2013 at the earliest.
Gif stolen from ebenetwo~