For one, WoW hasnt had any expansion packs yet and it holds 7 + million subs, how many expansion packs did it take for EQ2 to be a ok game now? I think When the burning crusade comes out it will fix ALOT of WoWs end game problems, for one all instances will now recieve difficulty settings. Blizzard has confirmed old instances such as DM and VC will have their settings tuned also.
Arena, a whole new explorable content, the regular world of azeroth is getting a 25% content boost. I think we should wait till the burning crusade releases to see WoWs true power.