More adventures are a good thing!
WotC SHOULD produce adventures, even if it's only one or two per year. Why?
First of all, there were scads of people that remember the days when 3E first came out- products assumed that you were using the three core rulebooks and that's it. Sucks if you were playing a psionicist, the only options you had were in the Pisonics Handbook. That's it. Recent products have included optional material, such as the new psionic powers and the like in products like Frostburn. Cross-promoting is good from a product design standpoint (why pay $30 for a book that doesn't mesh with other supplements?) as well as building product awareness.
Second of all, the fan base has gotten generally older. Most of the serious players are the same people who have been playing since 1E or 2E. In Six plus years, I've still never met a DM who started DMing after 3E. Working 40+ hours a week leaves you precious little time to design adventures from scratch. DMs with jobs and other obligations love being able to pick up an adventure and run with it. Sure, I could flip through the stack of d20 OGL material at the game store, but quite bluntly I'd rather just buy an 'official' product (even if it's not exactly what I'm looking for), skim it for an hour and be able to run it. That's the market for adventures.
I loved the first adventure path series- Sunless CItadel and the Forge of Fury are genuine classics. Could they have been done better? Sure, every adventure can use a little tweaking. They're classics because a new generation played their first characters through them, (or like me) was pleased that D&D was getting away from all the bizarreness of late 2E and back to the good ol' dungeon. New DMs also need something to cut their teeth on, and adventures form the basic language of how D&D players compare their game experiences.
Again, WotC should make adventures. Lots of them! Furthermore, they shouldn't be mishmashes of the latest supplemental material, but should build on a story.
Just for the record, I loved Red Hand of Doom. Best WotC-made D&D product of 2006 without a doubt. But Expedition to Castle Ravenloft merits someone a swift crack to the jaw. I'm still looking forward to the new adventures coming up though.