I'm A Banana
Potassium-Rich
I think based on some of the comments at the Gencon Seminars when the Ravenloft Campaign setting comes out, we'll see it functions kind of like Gamma World. It's highly importable into any D&D 4e based game, however, it will have some of it's own unique aspects that change the rules up in certain ways to match the flavor.
Personally, I like this.
I'd rather see campaign settings as almost like playing a different game. I made the case during the run up to Dark Sun that if it feels like I'm doing the same things that I am in bog-standard D&D, but with an orange coat of paint, it's not very attractive to me. I look at campaign settings as opportunities to be different sorts of heroes.
Though I've got major issues with the collectability elements (however small) in Gamma World, it is otherwise pretty much what I would want from a "New D&D Setting." It certainly allows me to be a different sort of hero! And while the Ravenloft rumors I've heard are not very encouraging ("Play as vampires and werewolves!!!!"), I certainly think a gothic horror setting would only be improved if it didn't have to be tethered to eladrin and tieflings and dragonborn and all that. If I could play a doctor or a scholar or a gentleman-adventurer, perhaps struggling against a dark inner nature, with a saber and pistol, and going town-to-town with my crew of misfits to liberate people from various versions of Gothic villains, Victorian and Edwardian mad scientists and devil-summoners, that matches the feel I would want from a game with the Ravenloft title on it.
And if it was basically compatible with 4e, I could (and would) mix and match elements to my heart's content.
My only fear in that case would be that it's not part of the DDI. Which would blow royally. Though if it was just a "two books (or boxes) and out" strategy, it might not hurt that bad.