"We are being very sort of coy about it," Fellowes said at a "Downton" event in London, according to The Hollywood Reporter. "We don't know. We haven't had a commission. But I think it would be pretty odd if there wasn't."
Adds executive producer Gareth Neame, "We hope to have some news in a few days."
Related: Famous fans of 'Downton Abbey'
"Downton Abbey" just finished its third season in the United Kingdom and brought big ratings to ITV1. Fellowes says that counting delayed and digital viewing, the show brought in "just under 15 million viewers." Its over-the-air average was 9.7 million viewers, making it the biggest of the show's three seasons.
A Christmas special is set to air on ITV in December.