c0rd on 30 November 2009
I'd say 2009 is its peak. Although it had a rough start, the Slim / $100 price cut combo pretty much erased it by September. Its final 3 months in 2009 is going to be its best ever, by far - FFXIII in Japan, and Modern Warfare 2 in the west are the biggest HD games in each respective region. It will also see its first holiday at $300 - this isn't going to be matched in the future. With the losses Sony has taken this year, I'm assuming there won't be a price cut next year (though if they do, 2010 is the peak).
As for the Wii / 360, they peaked 2008.
