Update: Or not quite: he's tweeted this afternoon to say the release timeline of the update "has been slightly delayed. I’ll have a status update later today."
Original Story: Nelson tweeted overnight the update for the new 360 dashboard will start appearing in the next hour. It'll start appearing at 3pm GMT, 10am EST and 7am PST. The update will come with the Windows Phone 7 Metro look, new TV content providers, expanded voice support and Bing. You can details on what to expect from it here.