I've assembled a few additional charts concering the sales of each when launches are aligned. Each of these charts pertains to a line of best fit using different equations.
PS3 - Quadratic 360 - 4th degree polynomial
This graph obviously isn't practical for predicting the future of the 360 at all, but it fits the data reasonably well.
PS3 - Quadratic 360 - 3rd degree polynomial
This is much better at predicting a future trend for the 360 and actually is strikingly similar to the PS3's graph, albeit with a more shallow curve. This displays the legs of the 360 well so far.
PS360 - Both Linear
This trend displays the PS3's advantage YOY.
PS360 - Moving average (period 2)
This chart is all about averages. The 2-period approach, I thought, may fit well with the 360's polynomial curve.
Projections from the charts are ~8m for each console next year, I'm thinking ~9 million though.
