In fact, the PS2 probably enjoyed a halo effect with regards to DVDs--not the other way around.
This quote is absolutely correct in my experience.
The fact that the PS2 played DVDs was icing on the cake. It was used as a selling point for the system. However, because there will be no installed base of BR players, nor any solid library of Blu-Ray titles when the PS3 launches, Sony won't be able to capitalize upon Blu-Ray's inclusion in the PS3 in the same way they did with DVDs inclusion in the PS2.
Regarding the PS2, how many of us have read or overheard people gushing about how the PS2 "ALSO plays DVDs too"?
When the PS2 launched DVD was taking over the marketplace, and the fact that the PS2 offered DVD playback made the PS2 more enticing to buyers.
But this time, Blu Ray is not taking over the marketplace as DVD once was, so it's almost certain that most of the people buying the PS3 won't even care if it does offer Blu-Ray playback.. They will probably just want to know if it can play DVDs or not.
Sony (and others as well) may be giving the PS2 too much credit for the advancement of the DVD format and expect the same kind of phenomenon to happen with Blu-Ray & PS3, and they might end up losing a lot of money because of it.