Eidos Montreal's Twitter account has teased an upcoming, unannounced new project called 'The Fall' and while there have been no details provided with the tease it's likely we'll see the game next week at E3.
Are YOU ready for The Fall?
— Eidos-Montréal (@eidosmontreal) June 3, 2013
There have been no other Tweets from the developer concerning the project since the tease so it's unknown if The Fall is the title of a future Deus Ex game or an entirely new franchise. In March the studio did however register several domains for Deus Ex: The Fall suggesting that it's highly likey this will be the name of the next entry in the series.
Either way, whatever they're working on will likely be headed to PC and next-gen consoles.
The studio has previously developed Deus Ex: Human Revolution and is currently working on Thief 4. Human Revolution was widely praised upon its release although the game's boss battles – which were developed externally – were criticised.
Human Revolution was a prequel to Deus Ex and Deus Ex: Invisble War but it's too early to say when The Fall will be set in the Deus Ex timeline. Hopefully, we'll have more information next week.