It depends. If it doesn't cost too much, I guess they would. I think it'd mostly be newer stuff though, unless they release the older games at a super budget price.
I don't think titles like Dead Space or Conduit would be viable at $50. Especially Dead Space. Nobody has been silly enough to put out a rail shooter on the HD twins because they know the genre is totally dead. I don't think it'll sell at all on the PS3 unless it's a budget PSN game for like $15... plus, does the PS3 Arc have a pointer like the Wii? I think stuff like Little Kings Story and Muramasa would sell on PSN, but those games don't make use of motion controls so technically they could have come over already if the devs really wanted them to.