There are several reasons why Uncharted 4: A Thief’s End had to be delayed. One of the major reasons was because Naughty Dog wanted to fix the ending for the game.
The game’s director, Neil Druckmann, was interviewed by OPM (via GamesRadar) where he explained why the game had to be delayed in order to give the series a sendoff that it truly deserves.
Druckmann said fans should expect Uncharted 4: A Thief’s End to go out “on a bang“. He didn’t want to give away any spoilers, but he said the ending needed “quite a bit of work“. If the game was released in Fall 2015, Naughty Dog would have had to scale back its ambition for the ending. The studio decided it was best to delay the game instead to see its true vision of the game.
He then said fans will be disappointed about the delay, but this comes at a small cost so that Naughty Dog can give them an ending that the series truly deserves.
You can say Naughty Dog did the right thing by delaying the game. Many people were disappointed that Metal Gear Solid V: The Phantom Pain feels unfinished even after you complete it. Hopefully Uncharted 4: A Thief’s End has a more conclusive and satisfying finale.