In Training posted:

http://www.eurogamer.net/articles/2017-01-30-dont-expect-another-deus-ex-game-anytime-soon

"These plot points were intended to be resolved in a third game, which would also complete the trilogy of Deus Ex titles begun by predecessor Human Revolution.

Much of this remaining story was once intended for Mankind Divided, Eurogamer has heard, until the game grew too large in scope and had to be curtailed. (Even with this, Mankind Divided's development took five years). It's unclear if this untold story will now be left unresolved - or tied up in another medium, such as a graphic novel."

Deus Ex is dead again because Mankind Divided was half a game on purpose and now the other half will never exist and the entire team got moved to three different Marvel projects.