BOZ
Creature Cataloguer
I had posted this idea in another thread, but it was a bit off-topic. It was directed at Andy Collins (who may or may not have still been reading the thread at that point), but I think it has enough merit to get people talking about it enough to bring up its possibilities to more WotC folks. 

BOZ said:instead of attempting to revive product lines, have you considered going more of the Ghostwalk-type route? you know, release a single all-inclusive package book that details a particular campaign setting and what differentiates it from the norm. this would give DMs and players enough to start building on, and if they wanted more stuff they could seek out older edition product. this reintroduces the material without a large commitment from the publisher. if the demand proved to be great enough, you could consider providing additional material. Ravenloft (AFAIK) is still licensed out, but you could publish such a book for Spelljammer, Mystara, etc this way.