Obviously the energy consumption for bitcoin mining is a real problem, but you are assuming that in a near future this could not be improved with less energy consumption of bitcoin mining hardware or even by the use of green energy (which need to be improved too). Bitcoin by herself, is not the main problem here.
Maybe we as humanity should work on getting to better sources of energy, instead? One such option is to produce the energy with solar panels on Earth's orbit and the energy would be beamed using microwave technology to Earth's surface. This work is well advanced, you know, and it would really be green energy.
That's one of the keys but one of the main problems here are the higher taxes that governments want you to pay for the use of green energy, also the elevated price of hardware made impossible for some users to use it.