"Long time listener, first time caller". Just sharing my 2 sats:
While I find it stimulating, I think this discussion (and other similar doom-like scenarios) is somewhat irrelevant in practice.
When the time comes and if we start seeing issues with block rewards being too low to maintain acceptable security, we're going to have multiple solutions being implemented for it, and definitely a hard fork to indefinitely maintain some degree of block subsidy is going to be within them.
If it is indeed confirmed that the original chain is now insecure, consensus should eventually coalesce in one of the hard forks that can actually keep moving forward with some degree of security assurance.
I feel like people sometimes think of these systems as when they fail there's a full loss, but that's not the case as the history is not lost, and so we can move forward from that history with multiple alternatives and allow the social/economic consensus to dictate which one becomes the new accepted chain.
The genie is out of the box, and some chain whose history is prefixed by Bitcoin's current chain history will always exist.
The only type of problems we should truly be worrying about are ones that might invalidate the security of the history itself, like a cryptographic breakthrough (quantum computing for example) that would turn some or all utxos into "anyone can spend".
Transitions might be disorderly and filled with drama and discussion as the "block size wars" in 2017, but anyone who doesn't want to "vote", can always just keep their utxos frozen in place while the drama sorts itself out, and maintain whatever holdings they previously had on the new accepted chain.