Edit: Sorry I should have said my predictions are for USA only.

My amateur predicitions and reasons:

 PS4 (USA):  350k
 XB1 (USA):  240k
 WiiU (USA): 110k

PS4 seems to be still selling all they can ship so I think there is pent up demand on top of what consoles normally sell in January.

XB1 seems to be well stocked in late December so I think demand will be pretty normal for January, and $500 price tag will go against it.

WiiU has been boosted by SM3DW so it will have it's best non-holiday month to date.

Whadja think?

Edit: USA

Wii U: 300k

Ps4: 700k

XB1: 500k

ps4 - 700k
xbone - 500k
wii u - 300k

Sorry I meant for USA.

For WW I will go with:

ps4 - 700k
xb1 - 500k
wii u - 250k

If you are talking monthly 

Then the month of January (WW)

Wii U- 600k

PS4- 900k- 1 M +( Can't remeber if it's released in Japan in this month)

XB1- 750k

If its just USA,

Sony hasnt shown they can put out good supply really in the NA region, I would say for the month of January 2014

WiiU: 110K
PS4: 400K
XBO: 500K

Why such low expectations for Wii U? , though I understand why you have Xbox 1 above Ps4 :3

USA sales in Jan are usually 4 to 5 times lower than Dec.  The best January for X360 was about 390k - which was coming after a 2.1M December.
I don't think a $500 XB1 will beat that.

I predict a remarkably similar set of numbers between the systems...

US:

Wii U: 190k
PS4: 250k
XBO: 270k

WW:

Wii U: 500k
PS4: 520k
XBO: 470k

Wii U: 175k
PS4: 225k
X1: 245k