Well I for one think this wont happen Blizzards Diablo III team likes the art direction they have ended up with.
They like it because they are a bunch of childish super nerds that don't know any adjective besides "awesome." Without harsh fan feedback, they would make everything look like lego star wars (a game I happen to love).:offtopic:
sorry for the rage, but its how I feel. I don't care if DIII is the greatest game ever, I still wouldn't hang out with any of those guys. (And if they tried to hang out with me, I would make up lame excuses).