Neil Druckmann, Creative Director at Naughty Dog, has today revealed how long the team at Naughty Dog has been developing The Last of Us for.
According to Naughty Dog there are two separate teams working simultaneously at the company meaning that they can work on Uncharted titles and The Last of Us. Druckmann commented that The Last of Us is “Naughty Dog’s 4th franchise and the game I’ve been working on for the last two years.”
So it seems the game is well into development which most likely explains how the trailer was in game footage.