If AI fulfills its promise and we get superintelligence, humans will not be capable of contributing anything of economic value via thought, possibly outside of small, comstrained niches.

You may as well try to outlift a crane.

Either this whole AI thing fails, and we never make the last small number of breakthroughs (or scaling) that gets us intelligent machines, or the obsolescence of the human brain is inevitable.

I'm betting that machines are going to end up intelligent, at least in the moderate future.