I think that because of no $199 deal the PS4 will be down MoM (it normally would be up), but because the XB1S has been $199 since October and wasn't that popular at that price, I don't think it actually played as big a part in December as the "price frenzy" of BF/ CM.I'm having a hard time with PS4 numbers... one side I'm thinking like you... no $199 deal = lower numbers.
But it was up YoY every month this year without any kind of deal... so why December it will be down?
December 2016 was 1.56m... I'm not seeing PS4 below 1.5m this month... it is it peak year.
The XB1 "fam" will be impacted due to the lack of XB1X pre orders and the XB1S carrying its lack of 2017 buzz, so I think it's going to be Switch > PS4 > XB1.
As of now, until some potential ground breaking news from Abdiel, I think
NSW: 1.5m
PS4: 1.3m
XB1: 1.1m