In an interview with Vandal, Dishonored co-creator Harvey Smith confirmed he's working on a new unannounced game at Arkane Austin. He explained that he had recently moved back to Austin Texas after finishing up development on Dishonored 2 at Arkane's Lyon studio, who's currently working on Deathloop for PS5.
Harvey Smith said the following "I'm not on Deathloop, I'm on something else, working with the guys who made Dishonored and Prey."
Vandal later asked Smith if the soon to be Microsoft acquisition had altered anything at Arkane, to which he replied with that there's been no difference at the moment. He added that, of all possible partners for Bethesda, he'd find it difficult to think of a better one than Microsoft, ending the interview with "They fit perfectly."
While we wait to find out more on this mysterious game, you'll be able to play another Arkane game on May 21 for PS5 and PC called Deathloop.