It seems that the shot was taken from a playable level in the game, with Eurogamer analysing the footage and concluding that it was rendered at 1080p, something they call fantastic considering the near-perfectly rendered hair on Drake.
The trailer can be found below. Uncharted 4 is expected to release sometime 2015.
Update: Seems like a coder on Naughty Dog's team has decided to put the rumor to rest by tweeting the following:
"@ZirpPop Our U4 trailer is an in engine real game level running on a real PS4,Paolo.Our trailer doesn’t look good enough to be prerender CGI
— Corrinne Yu (@Corrinne) June 12, 2014"