This is a very good point. It's also worth mentioning the halvings; meaning not only are ASIC improvements going to hit a certain performance wall, also the rewards will get lower, pushing down the amount of miners running.

What I also don't get @OP: what's your issue of high energy usage if the miners often generate their own and / or buy it from renewable sources? ASIC development and operation literally pushes for higher efficiency chips and manufacturing nodes as well as construction of new renewable energy plants (on- or off-grid).