I do think it was a good thing for Sony to support the PS2 with games like GOW2 after the PS3's release as they seemed to realise that the Ps3 price tag was too high and it may take a while to take off the ground and the PS2 would support Sony for a while. What nobody planned on though was the sheer demand for the Wii. What this may have inadvertently done is gave these more cautious people another choice before deciding and with the Wii now proving it's not going anywhere soon and losing it's fad image it may just have backfired. Sony's brand is not as strong as it was at the PS3's launch.
What I do find a mistake on Sony's part tthough is just how their consoles are now seen as extremes where the PS2 is seen as a casual console and the PS3 is hardcore - I dont think brand loyalty is as important as casual gamers who bought the Ps2 cos it was the only console that either was the market leader or cos it had games like sing star, guitar hero and buzz.
I also question your statement that there's 120 million ps2 owners out there - the ps2 may have sold 120 million but I bought 4 as 2 broke and I gave one away, my brother bought 2, my wife had bought 2 over the years and her brother had 4, where I work has 3 - one in each fun room and so on. I think it's safe to assume that at least 25% of the 120 million were bought as replacements or bought by people who since then just couldn't care less about games anymore then i'd say 90 million is a better number. Now the current gen has already sold 51.09 million and I know a lot of those are to a new demographic but there's still probably at least a large portion of those 90 million already jumped into this gen - can you really see a vast amount of undecided ps2 owners wanting to buy in to the hardocore ps3 or do you think it's more probable that the hardcores have jumped and the main people that are left are the people wanting buy cheaper or casuals?