Originally the title was supposed to release February 23, 2016, but now Deus Ex will release August 23, 2016. That is exactly 6 months of delay.
Recently the pre-order program was cancelled and since one of the rewards was an earlier release perhaps that is a good thing.
The developer notes that the delay is because they do not want to comprimise on quality, via Twitter. Eidos further went into detail about polishing efforts via the official website. They continue to note that the goal is to improve the franchise in every way possible and the delay is simply due to polishing since the team “is proud of where it stands today.”
“We’re confident and proud of the game so far. However, as we are now playing through the game in full we can see that it will require more time in post-production for tuning, iterations and refinement to meet our high standards. In order to achieve this, we need to move the release of the game to 23 August 2016.
The game is in development for PS4, Xbox One, and PC.