The PS3 was introduced nearly 4 years ago. Yes, time moves on quickly. What I do remember from the PS1 to PS2 transition, however, is that virtually no store had Playstation 1 games in stock in 2003. The few games that were scattered around in specialty game shops were either sales of remaining stock or the late sports games. PS2 games are still readily available new, though slowly disappearing as well. The gameshop I order 'only' has around 600 titles left to choose from, of which half is used.
To be honest I see little to no difference between the two transitions regarding the older console. The PS1 was virtually dead in 2003-2004, and the PS2 is nearing it's end right now.
The only difference I see is where PS2 owners move to. Many go for a 360 or Wii. I'm still considering either the 360 or PS3, and the 360 still has a small edge to me. PS2 backwards compatibility could definitely convince me otherwise seeing I have quite the collection, but the additional $50-100 price tag the PS3 would need for that would scare away a lot of other buyers.
Sony didn't like cutting the BC either. If they did they wouldn't have included it in the first place, and it worked very well for the PS2. So well that Microsoft and Nintendo are actually doing the same. With the PS3 being very expensive to manufacture they simply had no choice but to cut the feature. The fact that they never included a full hardware solution in the European version confirms that - in Europe they needed to compensate for additional taxes right from the start. Think of it, developers are very happy with BC, which benefits Sony. Sony is very happy with BC for other reasons too: people are way more likely to upgrade from the PS2 to the PS3 and they earn on repressing PS2 game discs too. There are no downsides for them except the added cost for the console in this case.
To make a long story short, I believe you can blame Sony for a lot - including getting rid of BC to cut the price of their way too ambitious PS3 console - but I don't think you can say that they have 'killed the PS2' by doing that.