It's not Sony that will determine how long the PS3 lives, but the consumers who buy it. The PS3 is losing market share AND mindshare quickly, and is losing exclusives monthly. 3rd party companies can only hold out so long for an install base significant enough to sell their software to.
For the PS3, Japan is doing horrible, North America is doing below average, and Europe is still an unknown at this point.
For the 360, Japan is non-existant, North America is good, and Europe is average.
For the Wii, I don't think I need to mention how it's doing at this point. :)
Software Lineup -
http://www.gamefaqs.com/console/ps3/
http://www.gamefaqs.com/console/xbox360/
http://www.gamefaqs.com/console/wii/
Nobody is crazy enough to accuse me of being sane.