Don't forget that the PS4 launches in mid Feb in Japan, so Sony will want to keep back a reasonable number for that launch. I do wonder how many units Sony will keep aside for the JP launch????? 500k? and it seems that Sony can get on average around 200k units onto the market each week, while making sure there is enough units for the JP launch.
I've said that a gazillion times. Sony is keeping some stock from 1.4m produced/week for Japan!