World of Warcraft is several orders of magnitude more complex. There are thousands of games which are more complex than Farmville but less complex than World of Warcraft in between these two. Thus I don't agree that WoW today is "as close to a casual friendly experience as it gets". Case in point, the general assumption is that Mists of Pandaria will make WoW *more* casual friendly, which wouldn't be possible if it was already as casual friendly as possible.
That is not to say that Keen and all the people complaining about the next WoW expansion don't have a point. What is certainly true is that if you draw a line from Everquest to WoW 2004 to WoW 2011 (and SWTOR 2011) there is a clear and steady trend away from hardcore. The only mistake is to think that we are for some reason already at the bottom of this trend, and it won't continue from here on. There is no reason whatsoever which would prevent Blizzard from continuing this trend with *every* future patch and expansion, making World of Warcraft even easier and less hardcore every year. Just look at games like Free Realms to see how much less complex and more casual friendly a MMORPG still can become.
Where will that end? Unfortunately for the hardcore, they do not play Zynga games. I believe that to understand trends in gaming, you need to be open enough to try everything. Which is why I play everything from hardcore PvP games to Farmville, even if many of the games I try out turn out to be not to my liking. Because in this case Zynga games, unexpectedly, offer a message of hope for the hardcore gamers: The trend for Zynga games, and other Facebook and browser games, is to get *more* complex on average every year. It turned out that Farmville was *too* simple, and while easy enough for everybody to learn wasn't interesting enough to keep people playing. The much maligned casual gamer and Zynga games customer demanded something more complex. Which means the long-term trend points not towards a bottomless pit of zero complexity, but towards a compromise somewhere half way between Farmville and World of Warcraft.
Richard Garriott is right in saying that World of Warcraft isn't a casual game yet, but Keen is right in saying that WoW is getting ever more casual, and other games will follow in that direction. As much as some people would like to see online games as a lifestyle, the truth is that these games are products, and are subject to market forces. As a business decision, Mists of Pandaria is brilliant. Even if that means that the genre is moving away from what their most avid fans wish. History has a tendency to repeat itself, and what happened to movies since Jaws is going to happen to games as well.