I think with recent VGChartz numbers this is becoming pretty apparent.
I'm assuming Japanese big sales are over (wasn't it January their holiday time?) and sales will be pretty slow from here to the holidays. NEVER underestimate MS's ability to cut the price even further, and let's not forget the deadly combination of Halo and Natal.
I was pretty sure Sony would take a lead in early 2011 but now I'm not so sure.
Regardless Sony still had a lot of pent up demand (and from what I've seen the PS3 is in short supply, at least in the US) so they will still make a strong push.
In the US the 360 will win pending the impact of their Spring line up versus Sony's Spring line up and how strong Natal is.
Others Sony should maintain a slight lead.
Japan is obviously a lost cause.
Overall MS will still take second place from Sony.
It's just that simple.