In point of fact, yes. Blizzard didn't start from scratch with World of Warcraft (in fact, many of their designers were actually players of other games, including Everquest and Dark Age of Camelot) -- instead, they (as they've always done with their games) took a formula and tweaked it close to perfection. And of course, since Warhammer is (if you listen to the hype) supposed to be WoW's biggest competitor going forward, it's not surprising at all that the ideas coming out of WAR are also making waves around the Blizzard offices.
That said, give WAR a chance.
Just because Blizzard's lifting the idea doesn't mean they're straight-out copying Warhammer -- as we noted, Lord of the Rings Online has the same type of achievements system, and Michael Zenke of Massively actually told me in their podcast that the Tome of Knowledge feature in Warhammer is actually much different (and better) from the "achievements" idea -- it's actually a record of what you do in game rather than a random set of goals to meet. So not only is it probable that the two systems will be very different from one another in function and implementation, but Blizzard had other influences as well -- they're not just outright stealing Warhammer's playbook.
I do think, though, as Syp says, that this is a sign that Blizzard wants to innovate and compete with Warhammer on their level. I'll leave it to you to decide whether Blizzard is "worried" or not about the WAR release -- Blizzard is the 800 lb. gorilla of the MMO world at this point, and any game with 10 million players doesn't have much to worry about any more anyway -- they've made their money, and even if Mythic steals half their customers, Blizzard has still made their gigantic mark in the record books. But I do think that it's a sign that even if Warhammer wants to be the shiny new online game this year, Blizzard isn't going to go quietly-- they're going to aggressively try to keep their years-old MMO on top of the heap.
Wrath is still in development, of course, and we may never actually see an achievements-style system in WoW. But why wouldn't Blizzard say this fall, as Syp speculates, "Why do you want to try WAR, when we have all of the features they have, and all of the content that they don't?" If WAR really is going to threaten their domination of the MMO market, wouldn't they push for innovation just as hard as Mythic and EA?