As it stands, the only confirmations we have are the releases that will be coming with newer games such as Fallout 3 and Rainbow Six Vegas 1 and 2. Sprinkle in the "this just came to Dashboard Preview" and I'm not really seeing near the list of titles you'd expect.
Well we know they will start with 100 games.
And I hope they will just announce each month a fixed number of games.
For instance they say they will add 10 games per month and announce them together with their Games of Gold annoucement.
I hope this happens at fixed times and not that we don´t know when the next batch of games will come, and threads start to pop up "When can we expect more BC games"