I am quite sure there will be more BTC hard forks with protocol changes. I have read some of the proposals. I don't think there has been much discussion on energy saving though.
There are dozens and dozens of theads discussing the energy consumption of the Bitcoin network and proposals on how to "fix" it - mostly by going from POW to POS but there are some others to be found with some searching.
Just search for "Bitcoin" and "POS" and you will find some hard fork proposals that might interest you but, of course, do not interest any of the miners who just bought ASICs.