Arkane confirmed that they aren't making another Dishonored so it's pretty much dead. Death of the Outsider definitely closed out the series but I don't think that was the original intent. I think Arkane was working on DLC for Dishonored 2 and when D2 sold below expectations, Bethesda told them that there wouldn't be a third game. The events that occur in DotO are way too significant to be relegated to DLC. They were likely intended for Dishonored 3 but crammed into DotO because Arkane didn't want to end the series with loose ends.
I don't remember them saying that the franchise is done,do you have a link to that?
As far as i know,during an interview they said that this is the end of Corvo,The Outsider and Emily's story arc but they want to make more games in the same universe.