In a new post on the Final Fantasy XV site, Hajime Tabata has revealed that the game will definitely be released in 2016, though the final phases of development will "focus on effort and willpower".
I vow to you all that every member in the team will do their best to the very last possible moment taking responsibility and pride in their craft. We will do everything we can do to finish FFXV to create an experience we are incredibly proud of and one that you will enjoy and treasure.
Read the full letter on the Final Fantasy XV.