One comment on the Undermountain stuff: from what I've seen and read, the Undermountain adventures at Origins and GenCon are adaptations of the published adventures in Expedition to Undermountain. Certainly you need a copy of the hardcover to run them (I think that copies will be provided to Origins/GenCon judges).
So it's not likely to be 'extra content' to any significant degree.
However the upcoming Living Greyhawk 'Greyhawk Ruins' mini-campaign is going to be extra adventures exploring less challenging bits of Castle Greyhawk (and, it sounds like, interacting with various Greyhawk City factions). The aim is to provide adventures which get PCs about half-way to the level they need to be to start playing Expedition to the Ruins of Greyhawk - so a Living Greyhawk PC would have to do some other modules but should have plenty of time before the Expedition is released for Living Greyhawk play, something I don't really expect to happen this year.