It sounds like we might be in for a long wait before we see another Deus Ex game, despite the fact that Human Revolution left plenty of plot threads to tie up. Eurogamer is reporting that the bulk of Eidos Montreal's resources are now focused on Shadow of the Tomb Raider, the title of which leaked last October, while a smaller team is working on the Avengers project that was revealed last week, and still more are working on an unannounced Guardians of the Galaxy game.
This is largely because Deus Ex: Mankind Divided, despite much hype and coming off the success of Human Revolution in 2011, was not a big seller. And despite the need to address those plot threads, the two follow-on story DLCs are dedicated exclusively to stand-alone stories—one is about robbing a bank and the other, coming in February, is a prequel story about Adam Jensen's first mission with TF29.
The report was backed up by Kotaku, which said its own separate sources indicated the same thing: That Eidos Montreal is focused on Tomb Raider and Guardians of the Galaxy, and is lending a hand with The Avengers. That can't be good news for the future of the Deus Ex Universe, which Eidos Montreal boss David Anfossi described in 2013 as "an ongoing, expanding and connected game world built across a generation of core games."
A Square Enix rep said the publisher had "no comment to make on this story at this time," but Eidos Montreal issued a statement to Eurogamer saying, "While we are still working on expanding the Deus Ex Universe, along with creating new content and updates for Deus Ex: Mankind Divided, we're also devoting our talents towards working with Crystal Dynamics and Marvel on The Avengers project."