Let's compare the first two weeks of December 2007 to January 2008 in order to form a baseline expectation for January 2009:

VGChartz Hardware data for the period 08th Dec 2007 to 15th Dec 2007:

VGChartz Hardware data for the period 05th Jan 2008 to 02nd Feb 2008:

As you can see, January sales are not that different from the first two weeks of December. Here are the first two weeks of December 2008, which should provide a rough idea of January 2009 sales:

VGChartz Hardware data for the period 06th Dec 2008 to 13th Dec 2008:

Wii supply will probably not be big enough to get these sales. As for PS3 and 360, I don't know what to say. It would be interesting if the gap was that big in January

Do you think these are reasonable predictions of January sales?

He who wins Christmas, goes into the new year with a lot of momentum. It will be interesting to see how many PS3s can actually sell at that price after Christmas burns through many of the people willing/able to purchase consoles at the higher price. I expect them to be down by 40% YOY.

Xbox 360 will be up YOY and ditto with Wii im guessing.

Is this trend also consistent with the first two weeks of December 2006 and January 2007 sales?

360/Wii up YOY and PS3 down is a sure bet. PS3 40% down YOY would be quite severe since it's down around 25% during the holidays. If you're right we're in for an interesting January.

I think 09 will be even more jumbled than 08 was tbh, its getting hard to predict these things this gen! I'm sure you could trend in the 08 holiday sales into early 09 but I am less than certain that it'll be the same as last year.
We'll see in a few weeks though!

VGChartz Hardware data for the period 09th Dec 2006 to 16th Dec 2006:

VGChartz Hardware data for the period 06th Jan 2007 to 03rd Feb 2007:

For some reason it seems 360 is lower in January in both cases. It still gives a pretty good idea though.

Look at how severe the difference between the PS3/360 after last holidays was. The post Christmas sales magnify any trends shown during the holiday season. I mean the PS3 only beat the Xbox 360 by 200k last holiday season and yet the first few weeks did that again and outsold the 360 significantly. So if the PS3 is down 20-25% over christmas they will likely be down by even more over the new year. If the Xbox 360 is up by 50% over christmas they will probably be up by 75% over new yearl. Well basing it on the past year anyway.

Well remember MGS4 didn't sell as many systems as we though...  as did most games... which seemed to create a slow rise effect rather then a "Oh shit the games out I gotta buy that system now!" effect.

If so.  I suppose that could be used to explain some more of it being down.  Though Sony does have some fairly big First quarter releases that should help lessen such an effect.

We must also consider the financial crisis, which has surely put a big anchor on PS3 sales lately (despite certain people denying this is so, it won't just suddenly start selling half in a matter of weeks) and any and all remedies for that coud change the outlook of things in 09, especially the last half of the year!

1/ yes PS3 will be behind, definitely. Same patern that the current holidays but with less absolute numbers for each console.

2/ this time the HD DVD will no have any potential impact on PS3 sales

(HD DVD died 06/01/07)