As the recent linked auction house feature has shown, sometimes it's the smaller things that make the biggest impact. A new feature that looks like doing just that is adjustable difficulty levels for the five-person dungeon instances. This will allow the leader of the group to select whether a dungeon is normal level or two difficulty levels above. But just so that the extra challenge is worth it, the potential spiffy loot-droppage will also increase.
Ah, there's just so much to tell you about and only a finite amount of pages to do it in. So if a new zone, two new races, a new profession, flying mounts and socketing wasn't enough, then how about five new spells/skills per class, two new tiers for the talent trees, teleporters that link cities together and outdoor arenas for gladiatorial style combat? Excited yet?
Well, sorry to have to dampen your ardour, but one of the things that the developers aren't forthcoming about is a release date. "This year" is the best that could be dragged out of Pearce. It's pretty annoying to have to circle almost half a year's worth of calendar in red. But just because it's you Blizzard, we'll do it. After all, you took our lives and you made us heroes.