The Nintendo consoles will fall furthest. A much larger amount of their sales were to parents buying consoles for their kids for Christmas. Those sales will fall away after Christmas and the figures will drop down to the regular sales to gamers.
360 will be the next one to suffer I think because it's heading towards a relative drought when it comes to selling points. All of its top games came out three or four months ago and it really has nothing going for it in the first half of next year - anyone who wasn't convinced enough to buy a 360 when Bioshock, Halo 3, PGR 4 and Mass Effect were released isn't going to buy one any time soon when there's no new blockbusters coming for quite a while.
On the other hand, the PS3 is getting stronger all the time. The huge amount of negative PR is starting to lessen, and in its place is a lot of positive publicity as PS3s are getting into consumers hands and people are starting to try games like Ratchet and Uncharted first hand. Add to that the fact that the PS3 has the Euro release of UT3, the Western release of GT5:P, the worldwide release of Haze all coming in the early months of next year and there's some genuine reasons for people who've been holding out to start wanting one. The release of GTA IV will do a lot to sway PS2 hangers on too, obviously its a 360 game too, but in a few months time when people are seeing GTA IV, Burnout Paradise and Gran Turismo 5 (albeit the prologue edition) all being released on PS3, regardless of some of them being on other platforms, that's a big chunk of the casual PS2 market that's going to take notice and consider whether its time to upgrade.
