You just haven't seen what I've seen 
Trust me, there is still a way to go with "graphics". As it was stated before by Darkstar, the PS4 can't easily push out 1080p at 60fps. It really does struggle. And that's not all there are to graphics. We could do with more photo-realistic textures, lighting, higher polygon count, smoother/more realistic animations, greater environment detail/depth, larger worlds, more gameplay mechanics (that don't get ditched immediately after introducing them) Call of Duty …okay so I strayed a bit from graphics at "larger worlds", but you get the idea. The only problem is that these things all take massive teams of people to achieve them, and with this we can expect fewer AAA games to be produced, and therefore larger gaps between releases. "Fortunately" Sony figured out a way to fill these gaps: Indies.