First block of proof. (I explain, why BTC in current state doesnt have future of 20 or 40 years, when all 21M BTC will be released, It will end much earlier).
Conclusion: mining is getting more and more pointless and that is happening in furious pace!
I understand that Bitcoin have its own end but no one knows when maybe it could be longer than 20 or 40 years. The price of Bitcoin dictates the profitability of Bitcoin mining and so far it's been that way for a very long time. If the price continues to grow we should be fine and as time goes by more efficient miners will be made to keep Bitcoin mining profitable. There's a lot of things that could change in 20 - 40 years.
We're still far away from mining all 21m and at that point there could be a better crypto that already killed Bitcoin or the majority continues to use Bitcoin .
Very good You mention some other coin will be killing BTC. Now moneywise, what would that mean for all "investors"? Losing their money, right? Now, just for second assume, that BTC was never meant to become a ready product. If it was designed to be money collector. What would it make BTC then?