Recently it was leaked that ME2 was getting a new dlc, well xbox360achievements got more on the scoop on Arrival with a little chat from Casey Hudson.
The details so far:
It is the final story driven DLC for ME2
It's about the impending Reaper invasion
Admiral Hackett is back!
It is 560 MS points

As the Reapers prepare to make their return, Shepard must decide how to deal with the threat in Mass Effect 2: Arrival, which has been confirmed as the final mission for Mass Effect 2. Sent to the edge of the galaxy, Shepard must rescue an undercover operative with evidence of an impending Reaper invasion. Fan favourite character Admiral Hackett will make a comeback in Arrival too, voiced by legendary gruff sci-fi actor, Lance Henriksen of Aliens and Terminator fame.

DedValve via xbox360achievements.org »