Just a heads up that the Traitor's Keep DLC is out now, BUT!!
It isn't advertized in the game, nor on Game Marketplace yet. Instead, the only way to get it just now is to go to:
Dashboard > Game Marketplace > Explore Game Content > Featured > Add-Ons For Your Games > Fable III > Titles a-z
It only shows up in that menu for now, along with a Free Soldier Uniform.
I can't say if it is any good or not yet (the uniform is spiffy though), I recently deleted all my heroes because I was bored with them, so I have had to start again lol.
I'm in the UK by the way, I don't know what the set-up will be for other regions.