I stopped buying D&D supplements quite some time ago, and see no reason to start again after 4.0 is released. However, I might consider Compendiums. The trouble is, most of the stuff I'd want compilations of is non-OGL. I'd love to see a Classes and Prestiege Classes compendium, a Feats compendium, a truly complete Spell compendium, etc. My biggest complaint with the Spell Compendium was that more spells were published after it was released. Now that all the material is basically finished, this would be the perfect time to publish compendiums. Unfortunately, WOTC doesn't seem likely to do this, and a 3rd-party company probably couldn't get permission for the venture.
As for adventures and locations, all my games use homebrew settings. The most fun part for me as a DM is creating these, so I have no interest in buying someone else's.