Better to focus on adoption rather than postulating what will happen 20 years from now, let alone 120 years from now. Shitcoiners love to use this as FUD but the reality is no one knows what will transpire.

I think we are underestimating what the potential use case for mining will be in grid balancing, carbon offsetting and what kind of revenue miners can generate from this as more things become electrified. Also mining being integrated into industrial machines and household appliances at no additional energy expenditure. It will be costly to retrofit existing machinery to do this but in the future new stuff can just have it built in from the start at nominal additional cost. Look at heatbit for an example of this (yes still way too expensive but over time that will come down and a mining appliance won't cost more than a non mining one so why not get the one that throws off a couple bucks in sats a day).

I also like the idea of insurance hashing. If Bitcoin is widely adopted and hundreds of millions or billions have a good portion of their wealth in bitcoin they are going to want to ensure it is protected so just like you would buy insurance to protect your house. Maybe hundreds of millions of people worldwide pay miners to hash to protect the network. This is better than tail emissions but definitely has some centralization concerns but maybe not if coupled with mass decentralized mining ala machine and appliance integration it works.

Or maybe 100M people have micro mining machines integrated into their solar, battery storage setup for their home.

I know some of these ideas seem far fetched but we are talking decades and a century into the future, it is hard to imagine what things will look like but I trust human ingenuity. If Bitcoin is successful, I trust humanity will find a way to make it work, enjoy the fruits of its success for maybe a century or two and then find a way to completely fuck it up.