Yes. But only in the perfect circumstance.
The problem with all 3 of our aging superstars is that their appeal is somewhat limited. Young teams probably don't want them and veteran teams who do want them don't have the resources we want.
Furthermore, we'll likely have to take on as much salary as we give up (assuming the other team is above the cap). But with KG and PP (Ray's not as bad), that's a lot of salary to take back. And that likely means one of two things:
1) Someone will try to dump their garbage on us, which we don't want (think a Rashard Lewis type contract).
or
2) Someone will try to give us a bunch of midlevel guys.
While case #2 might sound somewhat appealing, do we really want to tie up our financial flexibility on a bunch of average-to-good players making 5-10 million dollars per year? In most cases, that's a recipe for perpetual mediocrity in this league.
So, yes, I'd trade PP if the deal was right. I'm just having a very tough imagining a situation where it'd be actually worth it to trade him.