I've yet to see a single YouTube video that does justice to PS4 Killzone, Assassin's Creed 4 or even Lego Marvel Superheroes! To get my Bravia to look like YouTube representations of my PS4 games, I'd have to smear it in vaseline.
They don't, yet it doesn't exactly take an uncompressed feed to give you a clear idea on how it will look or where improvements have been made. In fact, the video is quite indicative (have you watched it?) because they switch back and forth between the PS3 and the upcoming PS4 version. Having owned and actually played the PS3 version, it gives you a pretty fair idea on what is lost through the compressed feed, but it also shows you that improvements in the new version are pretty much limited to textures, resolution and the hair. The rest seems pretty unchanged.
As I said, it's a beautiful game if you take last generation standards, but it's not going to look anything close to next gen. I'm guessing it'll be similar to what CoD:Ghosts (yes I own that one too) achieves over its PS3/360 versions. E.g. looks pretty much like a last-gen game.