4.2 million Playstation 4's sold since December 28th.
3 million Xbox ones since January 5th.
To put that in perspective if the Playsation 3 (Or 360 vice versa) had a 45% lead in sales over the Xbox 360, that would put it at 112 million consoles compared to 80 million.
When the Playstation 4 launches in Japan expect the gap to widen further, considering japan is what allowed PS3 to tie in sales with the Xbox 360.
Sony is shaping up to possibly reach Wii sale numbers.
This is going to be one hell of a gen.