In a pretty big leak of documents that have come from the FTC's court case with Microsoft, it's been revealed that Dishonored 3 is in the works.
Back in 2018, developer Arkane said that Dishonored was "resting for now," meaning it was moving on to develop other projects. That resting period appears to be over now, though, as over on Resetera it's been spotted that a series of documents revealing all sorts of confidential information from Microsoft has been leaked. This includes a lineup of games currently in the works at various Microsoft owned developers, and notably it mentions Dishonored 3 could be released in 2024.
Now, that should come with a big asterisk as it feels pretty unlikely that Arkane would announce and release a game all within such a short timeframe. Not only that, the document notes that Starfield and Redfall were planned to release in 2021, but both were initially announced as releasing in 2022, later being delayed to 2023. On top of that, the untitled Indiana Jones game was also slated for 2022 in the document, so it's probable that this document is a bit outdated.
Dishonored 2 and its mini sequel Death of the Outsider were both developed by Arkane Lyon specifically, whose most recent release was 2021's Deathloop. Though the leaked documents haven't indicated whether Dishonored 3 will be developed by the Lyon studio or Arkane Austin.
The document also makes mention of a currently unannounced Doom game subtitled Year Zero apparently planned for this year, but with no official word on that one we can safely assume it won't arrive until next year at the earliest.
According to Tom Warren of The Verge, these leaked documents were apparently attached to a single file, and were incorrectly hidden and posted publicly. It's obviously a massive blunder, and Microsoft is yet to make an official comment on the matter, if it plans to at all.