...and if a current iPhone owner switches to an Android device, I doubt they'll stick around Apple services! Therefore, the iPhone is still cornerstone to Apple's growth, as it enables it.

You're right about switchers, but I wonder if this is a missed opportunity. If I switched to Android, I might still want to use iMessage. I'd probably still want to be plugged into shared photo libraries between family members. I honestly prefer Apple Maps to Google Maps at this point. But I'm not sure how Apple would monetize this, or if they'd want to give people any incentive to switch.