But first priority should be gameplay imo. Wow can no longer score cheap points as a semi social media. Ppl have smartphones, facebook, scype etc for that today. A modern mmo should be able to stand on its own feet as a game. People should log in becuase they feel a urge to slay monsters, not because they are bored and feel like checking out guild chat/friend lists.
Better graphic wouldnt hurt the game though. It looks like Starcraft 2 and Diablo3 support Normal mapping - a 3d standard which "bake" thousands of polygons into the textures. If possible WOW graphic could get a substantial boost if they could make it support normal maps i think.