I can still see the XOne take 2nd place before the end of the year. The gap could schrink to about 1 million by the end of September, with XOne tier 2 launch and games like Destiny. Besides i think VGChartz tracking is a little off.
It won't take a miracle for the XOne outsell the Wii-U by one million in the course of the last 3 months of the year, including the holiday's.