Sony usually keeps their console on the market for 10yrs ... I believe that what really slowed down the PS2 sales was the fact that this gen started in 2005 which i believe slowed down the PS2 sales considerably resulting in only really 5 good solid years of sales...
...I dont see new consoles releasing till atleast 2013 or 2014 or even later so that will mean that the PS3 will have about 3-4 more years...
You are totally mixing cause and effect.
Hardware sells because there is demand for it, not because Sony wants it to sell. The previous generation had to end because there was no longer sufficient demand for the PS2.
Also, there were only two earlier Sony consoles, and they also happened to be the two best selling home consoles ever in the history of gaming.
What do you think, what made them sell for such a long time? The magical "Sony" logo on their casing? Or the exceptional demand (which the PS3 lacks)?
Obviously, if it would be a matter of wanting really hard, every company would keep their consoles on the market for ten years, or more, too bad it is useless if people don't buy it.
Exactly WHAT will make people buy the PS3 for another 3-4 years, considering that even more successful consoles than it, lost momentum after a lot shorter time?