Well, I live in a small country, Netherlands. And not having internet reception here is kind of almost impossible. Although speed is not always 4G.
I am not sure wether Apple will allow 3rd party apps to be accessed by CarPlay. That would solve the problem of maps, as googlemaps does allow downloading of maps nowadays. So you plan a route and then download it and it is accessible even without an internet connection. Probably Apple will come up with a similar solution. Although Apple maps still need a lot of improvement.
I'll just wait and see what CarPlay brings and how it works.
@D