I'd say WoW is more like Supernatural (TV show). First they use the "mainstory" that they intented to tell (Warcraft 3 -> Wrath of the Lich King) so like seasons 1-5 in Supernatural. After that just keep going as far as they can and at the end attempt to wrap it all up.
Originally Supernatural was written for 5 seasons but it went on for 15 seasons in total because the demand was there.