I think divisibility will get in the way eventually. What happens when over a period of 200 years enough keys are lost to where there are only 10 million Satoshis left in active circulation?

Surely by then people will move over to a new chain, be it a fork of bitcoin or a different one entirely with new features, and history will have to begin anew.

There are billions of ounces of gold out there, and ounces can be subdivided as small as technology will allow without any one else having to agree to a protocol change.