The premise is an assumption that high technology culture will survive that long.
Remember Roman engineers, who built roads and aqueducts all over Europe and the Mediterranean, some of which are still in use today. I’m sure they thought Roman technology would continue to advance unbroken. Then there was this little 800-year Dark Ages thing.
This “historian” is ignoring the barbarian hordes now appearing to be about to over run Europe and the rest of Western civilization.
There is also the very real danger that high technology DOES survive that long.
If computers become self-aware, what's to stop them from deciding we are not necessary?