Vaguely interested, but I don't see it as a threat to WoW. I think it (WoW) is far more likely to lose subscriptions through Blizzard upsetting the fanbase than it is through any other game.
With that said, I think Warhammer Online, and the 40k one sound like they have a lot of potential.
Nah nothing will knock WoW off the top of the mmorpg ladder. Its just going to be like starcraft, people will play it for about a decade and then slowly the graphics will look so outdated[even though the gameplay is still good] that people slowly drift to different things.