One Redditor claims to have received a phone call on October 22, 2012 about the 10th anniversary of Xbox Live, letting the user know that he's "one of their most valued members." A few weeks later (aka yesterday), a package arrived containing what you see in the above image. A similar report comes via one Kotaku user.
The only official confirmation so far that something is up came from Major Nelson, who tweeted yesterday about the anniversary and promising news to come. It looks like this news has taken care of itself.