Who DOES Blizzard need to fear?

A few conversations of late have been about particular games coming that post a threat to WoW. This topic picked up steam again because of the announced delay in the release of the expansion. Some feel Vanguard poses a thread. Others feel Warhammer Online (WHO or WAR, depending on your mood) does.

I personally doubt either will strip away a significant portion of the WoW accounts.

Players, yes, but these players will do what they did when they jumped ship from UO and EQ too: continue to pay for their account. Maybe a few months thereafter they'll slink back or decide to close the book entirely, but I don't think Blizzard will feel a pinch. I expect them to say what SOE did when DAoC started taking off: "we're happy for the competition. it's brought more folks into the genre and therefore to us". Of course, I also expect them to very soon stop reporting their numbers in a way that is easily disseminated, maybe shut down the /who all command and therefore drive out those folks like WarcraftRealms and PARC who data mine for everything from number of hours played to favorite hair style. Public company after all, gotta protect the perception of the IP.

I, also, actually think Blizzard has more to fear from the fragmentation of the genre itself with the rise of casual-MMOs (yea, they exist), those focusing on today's tween players, and those environments from which strong communities, and then games themselves, have spawned. But that's not something they need chew fingernails on anytime soon.

What do you think? (feel free to comment here or at this F13 thread)