X360 is a 4 year old system heading into its 5th year its sales are not expected to increase in annual sales. The recent price cuts of the Wii and the PS3 are eating into the 360 sales.
The 2009 Xmas sales period for 360 should be well down on last year's Xmas sales. The gap between 360 and PS3 will close to around 5 million by the end of the year.