I foresee various things occuring:

Value becomes meaningless. Today energy prices are plummetting against Bitcoin and will continue to do so. Bitcoin's constant demand for energy will lead, over the next 50 - 100 years, to a world where energy is produced in such abundance that we can do anything we want for effectively no cost. If we can do / make / buy anything for effectively no cost thanks to this energy abundance, then if the network doesn't change mining may move to a "everything mines by default" model where everything that is able will mine Bitcoin in order to improve it's efficiency. This would make mining more passive instead of active, which will more easily transition to a world where there's no subsidy and ensure Bitcoin is sustainable even without subsidies or fees.

I see another possibility arising though, one where the code is amended to allow (perhaps regularly occurring) decimal shifts and perhaps even gradual block size limit increases. The latter is personal speculation, the former is something Satoshi himself said may happen: https://satoshi.nakamotoinstitute.org/posts/bitcointalk/46/

Bitcoin was designed with the ability to do micro payments thanks to the fact that 8 decimal division was built in from the beginning. But micro payments will become more difficult if the network continues to rise in value without decimal shifts to allow further division. Imagine if there were a BIP within the next 7 years that ensured that the block reward never dropped below 1 "Bitcoin" because the entire network instead has a 0 added to it. A limit of 21,000,000 becomes a limit of 210,000,000. All wallets would show a balance that was 10x the previous balance, effectively performing a 10 to 1 split of the entire supply equally, while the real result is that divisibility of the block reward is immortalized as having 8 decimal points of division.

In a system where these decimal shifts occur automatically, whenever the block reward would otherwise drop below the decimal say every 2 - 3 halvings, it would mean the network would never stop providing a block subsidy and will continue to double in value against energy input via the mining network in perpetuity.

There would be no worry of lost coins as there will always be more division, effectively this regularity of division makes the total supply of money meaningless except for the fact that the fixed limit on supply growth means it will never be debased, and people could more intuitively understand that the value of their (and everyone else's) savings will grow at least 10x+ (my math actually says 20x+) a decade if they just save more.

The majority of wealth in Bitcoin will never be spent. The majority of wealth will always be saved for the future. Humanity will learn to live more frugally and spend more time with each other and follow more meaningful pursuits than we do now. The world will be a better place for everyone globally.

Appreciate the discourse. 🖖🍻

It is my understanding that Bitcoin's are, and always will be, a free market good. As with all free market goods cost of production cannot be higher than the expected return on the investment necessary to make the good or production wouldn't happen. On the other side cost of production cannot be much lower than open market prices they would expect to receive for them or people will focus on making more Bitcoin through mining, raising the hashrate which raises the difficulty and thus the cost of mining until they reach equilibrium again. This is ensured to occur thanks to the difficulty adjustment, as the difficulty increases with the hashrate then only the most efficient miners will remain profitable and stay mining. Less efficient ones either die off or are forced to increase their efficiency to stay profitable.

Remember that there is no other buyer of excess energy, we will create abundant excess energy and as the value of the coins rises our drive to mine will rise with it. The halving regularly reduces the payment for that effort and increases the value of all coins compared to electricity.

Think about it like this, 1 Bitcoin costs roughly 3 minutes worth of all the energy of the entire network to create today. The amount of energy input is going up and so does the total value held by that energy. In 8 years of 15% annual growth the total amount of energy will likely be 3x what it is today, and the amount of Bitcoin given in exchange will reduce to only 0.78125 (7.8125 BTC at that point if the 10 to 1 split I am suggesting occurs across the entire network). That means that 1 Bitcoin would represent about 12.5 minutes of the total energy input of the network. If you held 1 Bitcoin from today, you would see it grow from being worth 3 minutes of the energy given to today's network, to 12.5 minutes of the energy input by a network 3 times the size it is today. That's 12+ times the value.

These effects are self reinforcing. I don't see anyway for them to be stopped, and it brings abundance to everyone faster than anyone expects.