What sin2beta said. I suspect part of the reason for a lack of DS3 support is that since PS3 games aren't playable, it's just creating extra overhead for developers for a feature that really has no purpose - the system, presumably, comes with at least one controller, soo...?
The only reason I can think of to gripe about it is that PS3 arcade sticks won't be usable, which is kind of a bummer for people like me that already have three of them laying around for different systems. They take up a lot more space than you'd think :p
As for PSN games, I'm reading a lot of very mixed info, partially because many sites are referring to an interview where Sony talks about how they'll be streaming older games, but since "older" isn't explicitly defined, a lot of gaming sites seem to be assuming that PS3 games are part of that plan. I'm not really worried about it, though - they still provide DLC, patches, and all sorts of good stuff for PSP games, and it's reasonable to assume they'll take a similar approach with the PS3.
I mean, you're talking about a company that only recently discontinued the PS2, which is remarkable (and awesome) considering how long ago it came out.