Actually, they make a point in the article that they aren't sure that WoW is increasing the number of online players of massively online gaming, but they are pulling in alot of players from other communities like Everyquest and such. It's more about the success of WoW itself, not so much a particular model. Although "online communities" is definitely the hot catch phrase.
It also mentions they are at work on their next expansion, but refused to comment on it. Something about implementing a "Bastid" filter that will limit the number of alts you can have, and greatly increase the xp required to level based on the number of alts you have.