I hate to say this but bitcoins security budget issue might not be as bad it seems since the world entirely seems to have its energy output shrink significantly going forward.

But even if world energy output stays the same or increases, and BTC security budget decreases, the marketcap will just adjust. I know its annoying to have this uncertainty, but the current halving schedule seems to be one of bitcoins biggest strengths, what sets it apart from other PoW coins. But i could be wrong.