I think its impact on the genre will fall heavily on 2 things:

Expectations and Implementation.

So far, the DF creators have done a great job of not allowing the hyperbole and propaganda mongering of gamers to effect their overall goal. Considering all the games that have come out in the last 2 years, and all the hyping they did, I’m thinking this could be a plus for them. Still, there’s little info about a game that comes out in a little over 2 months. It could also hurt them, initially. In the end though, word of mouth is a much stronger advertisement then any 4 page spread in Game Informer. So, I’m watching DF w/ optimistic intrigue, although I think the day of the “we want perma-death” player is long gone. With such a large “casual” presence in MMOGs, DF will not be the new … you know… top earner killer ;)