It's not unrealistic at all.
The PS3 sold 7.5m units last year (2007) and has sold 5.5m already in 7 months of this year, so is well on the way to selling 10-12m this year alone.
Don't forget that the price will drop and at some point in 2009, the PS3 is likely to be $299 if not lower, so this will spur sales as well.
IMHO, it could be between 35-40m by the end of 2009 and it will also be larger than the 360 numbers IMHO as well.
Prediction (June 12th 2017)
Permanent pricedrop for both PS4 Slim and PS4 Pro in October.
PS4 Slim $249 (October 2017)
PS4 Pro $349 (October 2017)







