Users aren't stupid though -- they know that fees are insufficient currently to incent enough miners to protect the network. So adopting your fork would be crypto-currency suicide. So the limit stays at 25 BTC per block, until block 420,000 and then 12.5 BTC per block, until block 630,000 and then 6.25 per block, etc.
Now let's say it is year 2024 and fees alone are seen as being way more than sufficient enough to support the level of hashing necessary to protect the network, so the fear of the loss of subsidy impacting hashing capacity is not a limiting factor. However, people who hold bitcoins include people who have lent their coins out to those who have borrowed bitcoins and need to repay loans (denominated in bitcoins).
Good point with the incentive for the miners. But imo there would be enough miners without the subsidy as well. The ration between the fees and the estimated transaction volume (not the output volume!) is roughly 0,005% to 0,01%. You can easily reach 0,1%, what would be 100$ as reward for a block. So one year ago the subsidy wasn't more in termes of USD and there were miners.
Presumably anyone borrowing bitcoins would require a clause in the loan agreement that if the subsidy were to be reduced (change in the money supply were to occur) that their principal and/or interest would be adjusted appropriately. If the subsidy is discontinued there would be little gain for those who have lent out their coins. And who lends bitcoins? The economic majority, that's who. So it is not in the best interest of any of the economic majority to change the rules as far as the rate of Bitcoin issuance -- towards either direction up or down.
I can't follow. Let's assume the price for one BTC compared to real goods is stable, if there is an subsidy. Now I lend you 100 BTC for 5% interest. If the subsidy would be abolished the purchasing power of my 100 BTC would gain 2.5% every year and the interest rate drops to 2.5%. If I lend you the money it would be the same for me but it arises a new attractive option. Hording! 2.5% with absolutly no risk. So it is good possible that many bitcoin owner refuse to lend what raises interest rates again.
I think this topic is highly complex because we can't ignore that bitcoin is not the only possible medium for borrowers. Even the supply of bitcoins determinable because the velocity can always change. And the number of bitcoins? It will never reach the 21Mio. because every year bitcoins vanish forever (got lost, forgotten password, sent to orphaned address etc. but we will never know).
Finally, I do not exactly know who decides for the Bitcoin rules. Highly complex.
On the other hand borrower would not like bitcoins. Price inflation is always good for borrowers and bad for savers. Price deflation is the opposite. But this is highly complex. With less lenders and borrowers bitcoins might lose on purchasing power