I guess the only thing that can be said at this point is to hope for yugoloth love in 2007...
The 'loth book is definitely the fiendish book I'm holding out for.
While news of these Codexes is enough to make me cackle with devilish glee... I don't think anything WotC can publish in 3e about demons and devils will ever surpass the fantastic work that is Faces of Evil for 2e PS.
The fact that it has Robin Laws attached to it makes me excited. He's done some great work and runs a great game (I was able to play-test Hero Wars with him in a couple of sessions).
... and I third the need for more stuff on yugoloths.