This is indeed part of the grand illusion in the field - that improvements in cognitive capabilities translate linearly into research progress. There are talks where experts report projections of RSI progress growing exponentially.

This is why AI companies use research in a deterministic and rigorous field (mathematics) as a benchmark - it creates the impression that humanity will achieve comparable progress in other fields.

Having said like, like for other fields (e.g. graphics), hardware capacity slowly increases, and new algorithms are devised, so there will hardly be a strict plateau.

I'm not implying that research progress will be necessarily very slow, but that it's severely misrepresented for sure.