I have the feeling that most analysts and people in the industry are somewhat underestimating the "PS2 effect". The PS2 is still going very strong and selling many more units than any other console (it sold more than 4m units just in the Q3 of 2006!)
This is a very interesting data and shows that people keep buying PS2 over the PS3: the reason? PS2 is really cheap now and games like FFXII, Okami, Bully, Shadow of the Colossus etc. are even better than most of those currently available on PS3!
I do believe this is one of the main issues for Sony: even a huge portion of their fan base still prefers to buy a PS2 today instead of saving money and wait till they can afford a PS3 tomorrow.... (like the egg and hen question ;-) ) yep, I have the strong feeling that the PS2 is going to cannibalize the PS3 at least for one or even two years (as long as software houses keep releasing such great titles on that platform) and when it ends, it will be too late for PS3 to catch up with X360 and Wii.