So if a bunch of miners drop off due to electricity prices or such concerns, the network will simply readjust and keep on going.
BTC has a lot of issues, but nothing forces it to be ever power hungrier. It can scale down the energy consumption and keep on existing just fine.
Bitcoin and other proof-of-work (no actual useful work being done here either, opportunity wasted!) based crypto-currencies increase the proof-of-work algorithms complexity factor as a means of controlling the rate. Bitcoin cannot scale up without using an ever increasing literal waste of electricity. Want a better system? make a new crypto-currency trust basis... (proof of stake, etc.)
https://en.bitcoin.it/wiki/Proof_of_work
https://changelly.com/blog/proof-of-work/#Proof-of-Work-Draw...
Yes, BTC is proof of work. Yes, complexity increases to control the rate. But that's it.
Complexity has nothing to do with scaling. BTC doesn't scale. It's fixed at 1 block per 10 minutes, 1MB per block. No amount of horsepower is going to give it more capacity, so BTC doesn't scale up by wasting more power. It stays the same.
You can see this in forks like Bitcoin Cash, which took the exact same algorithm, and forked the exact same chain, but gained less miners. After some time it readjusted, and BCH is perfectly functional with less miners than BTC.
I agree that BTC and its ilk suck in many, many ways. But saying that power usage must increase is incorrect. It can remain static or go down without changing the functionality or the capacity of the network to process transactions, because those things don't depend in any way on the hashrate.