I'm not sure at all, but whenever iPhone gets it, I assume it'll be integrated with Google Maps. One of the features you'll instantly love is having all your contacts stored. My car's GPS (which was $100 in November) can only store two -- home and work. I can input any address I want, but that's a little more tedious than calling up a contact. It also does points of interest, but the iPhone's integration with the Internet blows that away.
I do hope it's in the next version, but GPS is a battery hog. Mine is always plugged up because the battery might last an hour without it. I assume the iPhone would have an off switch.