Good grief. Really?
...
As far as world building goes, I hope, truly hope, that the DMG buries it deeply in the ground. If you want to build worlds, you don't need the DMG to help you with that. You never did. What you need the DMG to do is get you up and running as fast as possible. Expecting new DM's to spend dozens, or hundreds, of hours before play coming up with worlds is unrealistic and one of the worst things D&D has done for the past 30 years.
I don't play D&D to create imaginary worlds. I play D&D to have adventures and watch PC's grow and develop. All I need for that is a setting. Take whatever history that you have in your world that does not apply to my PC and keep it to yourself. I simply, completely do not care to waste my time with six page treatises on Elven tea ceremonies.
Three hundred years ago, unspeakable rites were performed on yonder hill? Fantastic. This factoid has nothing to do with any adventures I can reasonably expect to undertake? Don't give a rat's petoot.
Hopefully, hopefully, 4e will finally take the position that playing D&D should be about PLAYING and not writing amateur fanfic.