White Wolf is not turning Ravenloft into a World of Darkness game. These products will be constructed using the open-license D20 system rules, and will be 100% compatible with 3rd edition Dungeons & Dragons. They only difference between WW publishing them and WotC publishing will be the fact that the Ravenloft books won't actually have the D&D name on them. Just the D20 logo.
I'm personally of the opinion that this is a Very Good Thing, for both companies. Wizards of the Coast, who were not planning to update Ravenloft to 3rd edition, now have yet another product on the market that draws attention to them. White Wolf, on the other hand, has a larger aspect of the D20 market, which can bring them new gamers as well.
That, and as much as I like what Wizards has done with D&D, White Wolf definitely has a better sense of how to do horror, something that Ravenloft was lacking in many of its later products.
So I say, "Go!" Most reactions I've heard have been equally positive. I'm curious what everyone else here thinks.