There've been rumors for years, literally, that Microsoft planned to move its Windows Phone team under its Windows team with former Windows President Steven Sinofsky as the head of both products. Cut to March 2013: Sinofsky is no longer with Microsoft and Windows Phone still sits in the Entertainment & Devices division.
Many have wondered when/whether Microsoft ultimately do the same. I just got yet another tip just a few days ago that the Windows Phone team is in process of moving under Windows client. I'm still not sure whether I believe it or not.