Microsoft announced the addition of Last.fm, Facebook and Twitter at E3 2009, much to the dismay of ornery anti-socialites, promising a 2009 release for those services. With a beta reported to hit this month, it seems things are on schedule.
According to MTV Multiplayer, Microsoft plans to issue said beta publicly "middle-towards-end of October". That would point to a finalised roll out likely sometime in November, perfect timing for commercials that would air just prior to Black Friday's holiday shopping madness.
Xbox 360 Dashboard Update Public Beta (With Facebook) Coming This Month [MTV Multiplayer]