Although no release date is given (curses!), Channel 9 interviews Justin Robey and John Noonan who both worked on the Crackdown 2 game (one on the console version, the other on Windows Phone 7).
The interview is mostly an overview of both games and the future of Xbox Live services, especially with the advent of mobile gaming on Windows Phone 7. Near the end they discuss how Project Sunburst will feature "asynchronous multiplayer" gaming which basically means that your Xbox friends can jump in on your map and help defend your base while you're say, taking a nap. Sounds like a great way to start that synchronous mobile multiplayer gaming that we know is coming down the road and it's also a great way to gain points and achievements too.
Combined with the Bing maps & Geolocation integration, we have high expectations for Crackdown 2 and we hope the timing of this interview indicates it's near release.
Source: Channel 9