Well, this
sort of existed before, in the 2d version. But only insofar as 'losing is fun', really...
(The game's mandates and noble structure would, if the player didn't forcefully struggle against it, eventually guide them up the steps until they get the king; the king in turn would demand that the player mine further and further east until Adamant was struck; and once Adamant is struck, he would demand that it be mined until the fortress dies. Well, mining even one piece of adamant would doom the fortress eventually, but he'd demand more and more.)
...hmm, that was all spoilery once, but I suppose it isn't really, now. Anyway, the point is, there was an end condition. And eventually there will be again, where adamantium is involved... but since it isn't guarenteed anymore, I suppose the end condition won't be, either (though technically you can guarentee it by selecting a mountain tile at the largest size -- there must be one, singular square with adamantium in it in that area, so you're sure to have some. Good luck finding it or, for that matter, even just running your fortress at a decent speed at that size, though.)
But anyway, I suppose the game's motto is "losing is fun", not "winning is fun."
[ June 11, 2008: Message edited by: Aquillion ]