Not gonna predict any specific numbers because when I did it once it was awful, but I'm going with an easy XB1 win.
It looks like November's gap of 100k is accurate, and that's absolutely awful for the PS4. I don't just think XB1 will win December, I think from now on XB1 will win the majority of NPDs. IMO from now on out the only months PS4 will win is when there's a big exclusive release and no big exclusive XB1 release.