I can believe that psx had +100M users, ps2 +120M users and ps3 will have under +60M. People like ps3, but don`t like price. I think that ps3 will be at 199$ in 2011, and that wii will have a lifetime of 4 years (this is the time for digital tv be available for all), and most will have hd tvs by 2010, so I guess that wii2 will be out by 2010. 360 I think that it will be out until 2012, some lifetime that ps3. So, my expectations are:
lowest expectations:
ps3 90 M
wii 60M
xbox360 45M
total: 195M, about same sales as this generation
highest expectations:
ps3 120M
wii 90 M
xbox360 50M
total: 260M, 30% increased sales over 200M this generation.