As far as "generic" d20 stuff goes from Green Ronin, I'd count Freeport and any other "drag & drop" settings as generic. Hell, even Ptolus is almost generic in so far as you can plunk it down in any homebrew world without having to rewrite everything to accomodate it, even though it would be much harder to insert it in, say, the Forgotten Realms. Freeport is smaller and easier to implement, with less background assumptions, so it fits well in many homebrewed campaigns.
Actually, this is something else I'm interested in, besides adventures. Mini-settings. Cities, towns, and other regions that are developed in a way that makes them useful to a DM. Like the old Village of Hommlet, where every character in town had some kind of hook. I like the idea of "drag & drop" locations. It's handy, and it saves me a lot of work.
This might just be me, but I wonder if d20 has seen enough stuff aimed at players for now. There are all the race books, all the class books, spell books, feat books, etc. I'd like to see more stuff aimed at DMs. More books of places, characters, interesting items with their own hooks (one of the things I actually like about Weapons of Legacy), and the like. Another book of feats and prestige classes is the last thing we need. But if I could get a book of towns, all moderately fleshed out and chock full of interesting characters with adventure hooks? That would be groovy.
A thought on the apparent decline of d20: maybe everything's been done now. It takes some real creative work to come up with any new "must-have" products, now that we've got the Complete Book of Everything Under The Sun (volumes 1 through x), and a new edition may or may not break through the wall of "oh god, not another book of feats." Either WotC will be able to hold our attention by just the novelty of a new edition, or they won't. If they don't, the market will go to whomever can provide stuff that really grabs us and makes us say "I want to play that!"