Naughty Dog and several other sources have come out to say that the teaser trailer shown off at E3 2014 for Uncharted 4 was done in-engine, in-game, and running in real time on a single PS4. It was also done so at 1080p and 60 frames per second.
Naughty Dog:
"All footage you see in the trailer was captured completely in engine. That’s Nathan Drake rendered in 1080p full glory using the power of our PS4 engine. All footage you see in the trailer was captured completely in engine. We’re targeting 60fps for Uncharted 4: A Thief’s End and as you can see the visual fidelity for our character models will reach new heights. In fact, thanks to the power of the PS4, right now Drake’s Uncharted 4 model is over double the polygons of Joel from The Last of Us PS3."

Gamingbolt:
"They confirmed to us that the Uncharted 4 trailer showcased during Sony’s E3 2014 press conference was a part of an actual level in game. Secondly, they also confirmed that the entire trailer was running in real time on the PlayStation 4 and it was all in-engine."