I've always thought that WoW needed to do what EQ does and have the previous expansion(s) still have viable content to do during the current expansion. In ANY given EQ expansion, people are still doing stuff from the past 1-4 expansions (depending on era) because there are still things WORTH doing. Like permanent stat upgrades for getting all the achievements from a particular raid, for example, or overarching quests that still give a best-in-slot item even when the expansion isn't current anymore. WoW had a chance to do stuff like this with the Legendary Cloak and Legendary Ring by making them scale up and continue to be BIS later, but instead they just removed them from the game. Under these circumstances, and with no AAs or out-of-era content worth doing, people are gonna be empty-handed very quickly.