In an article on the International Business Times today, it was stated that 9 Million PS4 units and over 5 million Xbox One units have been sold so far:
“Asked about bridging the gap between the two console’s sales figures (Sony report 9 million units sold, Harrison says Xbox One’s figure is ‘north of five million’) he says: ‘Some analysts will suggest that we are less than 5% into this generation, so there is plenty of market opportunity ahead of us.'”
The article quotes an interview with Microsoft corporate vice president Phil Harrison from issue #296 of Edge magazine. If true, that gives Sony a commanding lead so far in this console generation, but also signals that the war is far from over.