Update: Looks like it's rolled out for a bunch of you. A screenshot from a tipster awaits after the break and let us know how you fared in comments! Major Nelson just tweeted it's rolling out to all users now, so go ahead and log in and you should have an upgrade waiting.
Update 2: Well, getting the update may be tricky, with Xbox Live inaccessible for many right now. Some have suggested signing in on Xbox.com and accepting the new TOS as a way to make it work on your console, but until tings are back to normal we'd suggest keeping an eye on the XBL status page.