I think what you're missing is that the iPhone's 'Maps' program is not a Google application.
It's an Apple-made program that just uses the map data from Google. The software itself is made by Apple.
So no, I don't think you'll ever see 'Google Maps 5' on the iPhone since it's never had Google's Maps on it before. But you may see the features that you like added to Apple's Maps in the future. But, of course, now we're talking about Apple and we have no idea what their plans are.