The sad thing is, I would totally buy a PS3 just to play the next GTA. Either that or a new PC. I think making it PS3 exclusive would be unlikely because of the proportion of the market it blocks out, but it would be well worth it in terms of playability (though they would have less capital to invest in the next GTA if they did that).
@Snoopy: Yeah, flying car hacks are for losers.