If it was the best MMO they wouldn't be doing everything in their power to draw the people who left back
[You must be logged in to view images. Log in or Register.]. Free cataclysm, free level 80, free name change, free server Xfer etc etc.
It will take a long time... but it will eventually spiral into a lot smaller playerbase. Plus they are working on a new MMO but not a lot of info about it out there atm.
EDIT: I do agree though WoW 1-60 was darn good... even TBC was actually really neat... Wotlk was when things turned sour for me.