The next game in the Deus Ex series has been delayed by 6 months, according to a news post by Eidos Montreal on the game's homepage. According to the initial plan, Deus Ex: Mankind Divided was supposed to release on February 23rd 2016, but after some internal testing of the game they decided to delay the release date to August 23rd in the same year.
In the news post mentioned above, David Anfossi explains that even if they are happy with the game so far, the studio wants to spend more time on making sure that the game meets their high standards.
Our aim is for it to be a worthy successor to Human Revolution, and to improve upon that game in every way possible. I know that expectations are extremely high, and we not only want to meet those expectations, but exceed them.