I guess it depends on what apps work with CarPlay or the Android equivalent. If I could connect my iPhone to my head unit and have it display and control my TomTom app then I would be over the moon. The TomTom app is better than every head-unit satnav I have seen to date.
I can imagine iOS and Android will have a SDK which will allows third party apps like TomTom to be used within CarPlay. They've already allowed access to music apps like Pandora and Spotify.