It's a living module that 'resets' every time it's played. Because this is based on the original, it means the NPCs shift and move in reaction to the PCs. It's quite obvious too since I recently played a converted I6 on Halloween (also, it's mentioned in the forward).
What makes Curse of Strahd different is every single bit of the original module I6 - Ravenloft is part of this new campaign module. That's not the only thing that makes this version different. Curse of Strahd is a full campaign that draws on previous iconic work like the Van Richten's Guides and other Ravenloft modules. I haven't read it because I'm going to be a player, but I have read the forward, some of the NPCs, and perused the book.
