The network running at 2% of what it is now is still quite a secure network.

Any change that does occur could be quite spread out (over even 20 years towards the end - there'll be enough time to come up with a plan for how to address these shortcomings).

What if each block contains 100000 transactions instead of the current 2800, little infrastructure change is probably needed to change that (if any other than code and signalling). Each of those could pay $1 and overpay on the current system.

Also, if you're using bitcoin and you're a large bank, a small shop or anything inbetween, what's stopping you from storing your own version of the blockchain and hosting your own node and miner? Even if normal miners are expensive to run, there are solutions like sidehack's range that just run off a usb socket (normaly) and don't consume much power - although their current offerings are much closer to the usbc type power usage afaik.