Character models will obviously always improve until they look 1:1 like a real human but the differences aren't that "important" anymore. It's not like going from a character looking like a stick to something better. Ok, facial movement is still something which needs a big push.
Where I still expect an improvement which does look as good as the one from PS3 to PS4 is the environment. Maybe it will be an even greater looking step with better lighting and better hardware to handle big landscapes.
Edit: or looking at the pic above me, it's time that not only the main "characters" will look good but also all the little stuff which isn't the main part of the game. Like all the animals or audience in a sports game.