I did a month by month fourier analysis a few months ago, but there are so many variables on console sales that can totally screw up the analysis.
IE:
Last generation, the PS2 had a very steady path for sales - similar to most other systems (Xbox, N64, PS1), in the fact that US sales for the EOY was very standard - it depicted a rising and falling of the peak sales, with years 3 and 4 (holidays) being the strongest. This is typical of most every system (save certain elements of the GC due to Zelda:TP, N64s OOT, and XBs H2 for Nov).
However, I never found any good-as-gold system for extrapolating a week to week measure of the end of the year. EOY Christmas sales are entirely determined by momentum and the right Holiday strategy, and not on a simple chart extrapolation.
A good example would be PS2 and X360 last year: both broke a few smaller molds on their sales. PS2 broke it because sales were so high for it's 6th US year. X360 broke it in the fact that it's EOY sales were quite a bit higher than the sales pattern through the rest of the year.
Likewise, it'd be hard to extrapolate where sales will be at the end of this year. Using very traditional analysis that wouldn't work; one would judge that the Wii will do 3m units in December alone in the US. However, production capacity cannot allow that. Likewise, these sales could go elsewhere (x360), or nowhere at all.
So then it's really just upto our prediction league ideas. There are so many variables and what-ifs for this Christmas, exactly like last year. Last year, X360 hardware was beyond mediocre, but the X360 managed to outsell any previous Xbox year in December. Likewise, Wii had one of the best first-December showings.
Basically though, for Oct-Dec, your sales will be anywhere from 6x (versus a normal per-month basis) on a very weak console, upto 15x for a very strong console. In the PS2's case, it was averaging about 300,000 units/month for many calendar months, and wound up with around 2.5-3.5m for many, many Nov/Dec NPDs. Likewise, October can be very telling, or not at all. October was a crappy month for the PS2 and X360, but both wound up doing great sales vs. October.
So again, it's all up to the prediction league. :-p
Back from the dead, I'm afraid.
