V1.0 would not be ultimate, it would be impossible. A game like DF is never truly finished, in a sense it's procedurally generated like the game itself, and will be for all eternity. I guess it's like Zeno's paradox, you can get closer and closer to v1.0, but never reach it.
DF is a paradox in itself. The most complex video game/simulation blend that we've ever seen, yet it's created by one single person living off of donations. It inspired countless intriguing and beautiful stories, novels, songs and works of art, yet the game itself has no sound, only one music track with one single acoustic guitar and it uses graphics that would've been considered ancient and obsolete more than a decades ago. It looks like it could be run on a NES, yet it needs the most powerful hardware in existence to be able to play the game to it's full extent. DF is immensely popular, yet it's totally obscure and unknown to the general gamer audience. Etc.
The evidence is clear: Dwarf Fortress shouldn't exist! It's unpossible!
Are you sure you know what a paradox is? Being unusual or doing unprecedented things does not make something a paradox.
A paradox is essentially a contradiction, something that should not exist, yet it does. I know what it means, the above post was merely meant to be sarcasm.
Generally v1.0 means the final, complete version of a game. in a sense, Dwarf Fortress will never be "complete", so in this regard v1.0 can never be reached. Of course Toady can use these arbitrary version numbers every way he likes, so this might not be case with DF, as 1.0 can mean just another stage in development (which it will, if I'm correct), and then 2.0, 3.0 and so on until Toady will no longer develop the game for some reason or other.
I rest my case.