More than half of all the 21million bitcoins that were ever designed to exist are already out there in circulation. Mining new coins is not important to liquidity, we just need to find 144 blocks each day for transactions to ride on, it no longer requires many coins in those blocks as we have enough in circulation, so it might as well just be the one coin. I don't think waiting until 2029 is the answer, the world will be struggling for oil and coal around then unless something else happens to curb world demand.
Oh.
You are suggesting a change to the protocol. Not just any change but a change that would cause a hard fork. And, not just any hard fork but a hard fork that would greatly punish the miners that switch to your suggested alternate protocol (only 1 BTC/block) versus staying on the original protocol (25 BTC/block).
So, it will
never happen. And just so you know when I said never, I meant never and there is no need to try to argue for the various virtues of the proposal - unless you actually like talking to a walls or trying to move mountains.
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.