IPv6 has a total of 3.4E+38 addresses, and the entire surface area of the earth is 5.1E+14m². If we divide those two, then we find that you can have 6.7E+23 addresses for every square meter of your Saharan desert or Pacific Ocean smart roads. If civilization doesn't collapse due to nuclear wars or climate catastrophes and we actually do make it to the stars, I doubt that we would still be using the centuries-old and deprecated internet protocol.

IPv4, in contrast, has 4.5 billion addresses, and there are currently 8 billion humans on Earth. While not every of them lives in the parts of the world with internet, that number will most likely soon shrink to nearly nothing. When everyone and their dog has a smartphone, laptop, desktop, console, smart TV et cetera, that 4.5 billion doesn't seem nearly as big as it first once seemed to be.

This isn't a Y2K-scale problem that will summon armageddon if we don't solve it immediately, but our current solutions to the overflowing IPv4 addresses are well-polished hacks at best. IPv6 will ensure end-to-end connectivity for many years to come.