The XBox 360 loses momentium every week because the mainly because the number of people who are willing to buy a $400 is pretty limited ... It will be years (and several price cuts) before the PS3 can even build enough momentium to challenge the Wii on a weekly basis.
The Wii HD may come before 2011 but only if the Wii has problems selling. It will (likely) be in a completely different price range to its competition which matches closely to people who don't have HDTVs so I don't expect "shiny graphics" will kill the Wii. Consider that in 2008 the Wii (with Wii sports) will likely be $150 or less while the XBox 360 is $250 and the PS3 is $400+.
If I'm correct and there is only 15 Million people worldwide who are willing to spend more than $400 on a game console how will the PS3 maintain third party support in 2008/2009?
