That’s a very good question Rob.
It’s highly debatable because I’ve been to highly impoverished countries like Nepal but they have broadband Wifi literally at the mountain top!
I think smartphones have a good long way to go still for mankind until AR Googles or other wearables become so good in battery life and cost that we no longer carry mobiles.
However, probably the mobile app scene will end up with a few giants for each category of use and the rest coming and going; just like websites today. Think search engine, e-commerce and payment dot.coms… where were we 15 years ago in diversity and now…