I think that rear bumper is just designed to move the NSX into more contemporary styling circles, with the exhaust tips protruding from the rear bumper. I kind of like the way it looks.
What I'd like to know is why the vents in the front hood? I'd like to think that they serve a purpose.. but I can't think of a practical reason for them, since the NSX is mid-engined. Possibly that these vents aid in brake cooling, generation of downforce, or perhaps feeding some crazy custom intake design (i.e. with the induction devices mounted in front of the crew cabin).