https://wccftech.com/xbox-one-39-1m-units-estimated/
Was a little excited when I saw this, but found out it was only an estimate. Seems about right to me, but hopefully Microsoft eventually releases sales figures for the Xbox at some point.
Edit: Saw the other post just as I submitted this one...
Made a bet with LipeJJ and HylianYoshi that the XB1 will reach 30 million before Wii U reaches 15 million. Loser has to get avatar picked by winner for 6 months (or if I lose, either 6 months avatar control for both Lipe and Hylian, or my patrick avatar comes back forever).