Since the reveal of Final Fantasy 7 Remake, Square Enix has shared quite a bit on certain aspects of the game, but not on when it will release. Perhaps it's because the game has yet to reach a point in development where Square Enix feels comfortable announcing a release window.
As far as the development timeline goes, 2016 will be the year Square Enix 'prepares' Final Fantasy 7 Remake for development.
"I believe that this year will still be a year of preparations for Final Fantasy VII Remake," said producer Yoshinori Kitase according Famitsu magazine (via Siliconera). "I'd like to create a new kind of value for the hardware that is the PlayStation 4 for our next announcement."
This likely means that 2016 will be used to write the script for each part of the multi-part game (Square Enix knows how many parts the game is, they just haven't shared it), get storyboards fleshed out, voice actors in line, set the game direction and more.
Using 2016 as a 'year of preparation' and 2017 as the year of development might hint at a 2018 release, but looking at past Final Fantasy games, the development might take longer than a year. Hopefully Sqaure Enix takes their time and makes it an awesome game.
