The same guy who leaked the (now proved accurate) deets on the Rebellion Pack just posted more DLC info:
Mass Effect™ 3: Earth:
The fighting is fiercest when it's your home at stake! Mass Effect 3™: Earth adds mods, gear, and new maps for Rio, Vancouver, and London. It features 3 new weapons: Piranha assault shotgun, Acolyte pistol, and Typhoon light machine gun. Six new human N7 classes are also available: Destroyer, Paladin, Demolisher, Slayer, Shadow, and Fury!
And as a bonus, Mass Effect™ 3: Extended Cut:
An expanded ending for Mass Effect 3. Additional scenes and an extended epilogue reveal the impact of Shepard's choices on the future of the galaxy.
(Nothing that you guys didn't already know about the Extended Cut, but it's at least done.)
SAUCE Apparently they will be 2 separate expansions, not lumped together. I'm trying to not be super negative about the ending DLC but my preemptive reaction is one big "meh".