First, background. I played WoW for 6 years (maybe 5, with time off counted out). During that time, I dabbled in many other MMOs. All of them lacked certain things that WoW did really well (crisp controls being a major factor), and inevitably I ended up back in Blizzard's pocket.
Then I heard about TOR. If there are two categories of media I love, they are 'Star Wars' and 'BioWare video games'. I've been following TOR, with varied levels of enthusiasm, for three years. For me, all BW has to do is get the controls CRISP, at least as good as WoW, and WoW will take a serious hit. The rest of the game will exceed WoW's play in every way.
I didn't know about GW2 until about 3 months ago, and only recently started looking into it seriously.
It will, without a doubt, destroy and revamp everything about how MMO combat and mechanics are done. If the events system is as good as it sounds, it will do the same to quests.
GW2 and TOR will signal the end of WoW's MMO market dominance. D3 and rumors of Titan will aid. Of the two games, I think GW2 will be a better experience. The controls, animation, art, combat mechanics, and depth of world look too good for TOR to match. TOR will probably have better immersion and storytelling, and good combat of its own; but for those of us who avoid 'more of the same' mechanics, it will appeal to us only by its 'secondary' qualities (story, setting, etc).