I'm going by shipped for simplicity.
2005: 1.5
2006: 6.7
2007: 9.3
2008: 10.8
2009: 10.2
2010: 12.1
2011: 2.7 (1Q)
Total: 53.6
X360 just had a record Q, shipping 1 million units more than it has in any other CYQ1. MS expect good momentumn coming out of E3 and going into 2012 (Price cuts duh)
So, although possible, it's unlikely they'll be down much over the collective 3 Q's coming up. Pitting them at just over 64 Million units shipped.
It would also put sales for the year at 13.3M, hows that for a 3rd, 4th, 5th, 6th year peak 
I doubt 2012 will show huge drops, nothing below 2007 levels anyway, so 75 million plus is a good guesstimate.
After that I guess it depends on MS's support of the system.
I reckon if 2012 has good support and it doesn't drop like a brick, 90 mill lifetime is achieveable
2011 - 13/14
2012 - 10/11
2013 - 6/7
2014 - 3/4
2015/2016 - 2/4
Total 86 - 91 Mill
Where do you think it'll end up?
