THAT'S where the Mongrelfolk appear! That was a long time coming!
One reason I have mixed feelings about Chris Perkins DMing COS on Twitch! 1. How are we mere mortals to compete? 2. SPOILERS.
That being said. I am hanging out to watch it. Chris is a kick ass DM.
It must become part of a grand story if they want to re-sell you more Ravenloft at a later date. It's the same with Magic the Gathering: Resell the same mechanics again and again, just with refreshed artwork and refreshed hype.
If they were to give you "one true settings book" at $50, then they're done. Kaput. "Expansions" and "fantasy novels" won't sell to fans, because the fans already have the "one true Ravenloft" book.
But if they only give you one adventure path at $50, then next year people are hungering for more Horror and Terror, then WotC can put out another $50 adventure path. Then the next year, Star Wars: the Terrible Mists movie is released, and WotC sees enough market to put out another $50 adventure path to cash in on all the hype.
I guess I'm saying that "hype sells" and "one true core book" ends product lines and kills the IP.
In Chris Perkin's impromptu AMA last night that was broadcast in lieu of the adventure at Lights, Camera, Action (the had technical issues), he stated that one of the reasons that they are not publishing an entire setting is that they opened the setting up for fans to publish the own material about and set in Ravenloft in the DMs Guild. Whether that satisfies or upsets those wanting more campaign material for this setting, will depend upon the quality of what is published and how strongly one feels the need for "cannon" material.
One can argue about whether WoTC has a good business model, but I think that calling it "reprehensible" is a bit over the top. Curse of Straud is the only 5e adventure path I bought and I'm really enjoying it. The quality of the story and artwork is great. Maybe it is not what everyone wants, but it scratched my itch.