Soon as in this summer???
And do you know how it will work? Will it be one player from one guild vs one player from another guild? Or armies made up from several players military buildings?
I am curious to know!
From what I've picked up on the topic from the various forums (en mostly), it won't be direct attack but more of a Risk-type thing. Not sure how they're planning to work that out, but it won't be guild vs. single player for sure, and might even not include attacking/plundering with players, but more like fighting for some land somewhere? Just a wild guess.
Guild Wars won't come in the 1.06, 1.07, and 1.08 game updates, so I'd say end of summer / early fall is a good estimate on when they will come.