So the long awaited return to Omega. Announced Back in October at Comicon in NY. (Sorry for posting this just now) It will be hitting the systems(Yes all of them) on Novemeber 27th, for 1200 ms points or $15. Thought this has officially been known since Leviathan was released So we'll be taking back Omega from Cerberus, and possibly even have Aria T'loak as a temporary squad mate.
No. There has been a number of DLC http://masseffect.wikia.com/wiki/Downloadable_Content Look under the ME3 section. This is the third to add to the story. (I am counting From Ashes, as one way or another you did pay for it if you have it.) //Ignore this line. as it is a comment