Fans have believed this to be the case for a long time now.

For the longest time now, fans of Arkane Studios have believed that Deathloop takes place in the same universe as the Dishonored titles. Besides sharing some of that familiar Arkane gameplay style, the two feature a number of similarities. These range from certain environmental design elements to the fact that both games share some similar usable abilities like Shift and Blink, among others. A weapon in Deathloop, named the Heritage Rifle, even depicts the logo of Dunwall Tower from Dishonored.

There are a whole slew of additional threads that tie the two game franchises together, but nothing has ever been officially confirmed by Arkane. At least, that was the case.

On the most recent episode of the Official Xbox Podcast, Arkane Lyon studio director and Deathloop director, Dinga Bakaba, finally confirmed what fans already knew: Deathloop takes place in the same universe as Dishonored. Not only is it in the same universe, but Deathloop take place in the future of the Dishonored universe.

Jeff Rubenstein from Xbox asked Bakaba about the idea that Deathloop is connected to the Dishonored universe. Bakaba confirmed that this was indeed very true and went on to explain the thought process of tying the two different franchises together.

"Not everyone has seen the same thing. Not everyone has heard the same song that you might have heard hidden somewhere. Not everyone has seen every room, et cetera, et cetera. So, it was nice to see the community peek at the little clues we did sprinkle everywhere that, yes, indeed, we envisioned Deathloop to be happening in the future after [Dishonored 2's standalone expansion] Death of the Outsider."
Bakaba continues on to say that he and the team didn't want to make the connection too obvious. They wanted Deathloop to have its own story and own identity that was able to stand on its own. Even with that, they did find ways to explore a world that reflects what it would be like after the events depicted in Death of the Outsider.

"As we were making Deathloop, we said, hey, [this story] could be one of the things that could happen after [Death of the Outsider.] So, we have a certain timeline to link that and there are a lot of clues, actually, in the game. There are some that are abused, one of them is really spoiler-y, so voila, but there are a lot of small things and some that were under people’s noses all the time, but people are just figuring it out.(...)

"We tried to see everything as an evolution, but each time they mentioned the past, either we were vague enough or we disguised in, I would say, natural ways the names. Like, they talk about the Motherland, and not about Tyvia, but you can definitely… once you know, you can unravel everything. And yes, it does make sense. So, it was nice for us to be imagining one of the futures of the Dishonored world and to have that make sense."
Despite the variety of ways in which the two games are connected, each franchise are still very much their own thing. I personally loved both Deathloop and the Dishonored titles, but their core gameplay ideas are very different from one another. Just because you like one, doesn't necessarily mean you'll like the other.