The Age of Conan dev said it recently in an interview.
Nobody reads quest text. They just click the button, and wait for the reward. Pavlov at its best. Even with engaging story, and huge background of lore, folks just want the cookie.
I have my doubts that they will be able to even briefly engage folks in story such that they forget about the cookie you get when you pull the lever.
There are of course folks who care

but will it be 'enough'.
There is no doubt those guys can make a compelling single player game with deep story, but lets see them translate single player joy into an MMO fever.