From an economics point of view, my opinion is:
once the supply of 21m bitcoins is fully mined, the economic aspect becomes
a) the amount of demand for transactions
b) the supply of miners competing for those transactions
c) the difficulty in solving the problem.
If Bitcoin has reached mass adoption, demand will be ever increasing as transactions grow unless costs are too high. If costs are too high and this means the number of transactions falls, it is likely to be because people have moved out of Bitcoin and returned to fiat or converted to other cryptocurrencies or are undertaking transactions on a different platform. That could lead to a huge slump in value of Bitcoin and possibly its extinction
On the other side, if there are a lot of miners (very high supply) and the difficulty in solving the problem is brought down, transactions will be cheap enough to retain user transactions and there will be many many more transactions. This theoretically would mean that Bitcoin remains a transaction base of choice and miners would be rewarded fairly.
The latter option is likely to lead to only a few huge bitcoin mining farms who will have the economies of scale to deliver to be able to make money from it.
The other aspect is that the computational difficulty would have to be manipulated down to reduce energy required to deliver a transaction.
Sound realistic? Or will blockchain massively disrupt theory of economics and bring about new theories?