Alternative theory: there will continue to be bad programmers, but there will also be good money in compilers that can deal with it and turn crap into optimized goodness. Midas compilers.
I also suspect a few new language concepts (like Rusts ownership model) will need to be invented as well, to enforce certain optimizations with minimal cognitive load on the developer.
No amount of compiler optimization is going to fix algorithmic failures.
Optimizing via better algorithmic choices is a semi-deterministic process performed by a human. Why can't a computer do it too?
Code is just your way of telling the computer your intentions. Once it can understand those deeply, well, it can choose a better way to achieve those intentions.
Demand for new data models is insatiable and for each one, a software ecosystem can develop around a similar degree of automation, tuned towards the specific domain. It's a very, very black-boxed future.