Throughout history there have been some extremely smart people.Evolution is hardly done with us. If we manage to outlive our various foolishnesses, our daughter species may be enough smarter than us not be be a danger to their own existence.
Moses comes to mind. He invented the Hebrew characters from Egyptian hieroglyphs and used them to record his many rules and laws and an account of his history in Egypt, Median, and Sinai. He also invented a narrative of his ancestors.
Homer also comes to mind, regarding the war chronicles of the Greeks against the Trojans which we call the Iliad, and also the adventure novel and love story which we call the Odyssey.
Egyptian mathematicians and geometricians as well, and Babylonian astronomers, and Egyptian and Greek physicians, and Greek philosophers, and scientists beginning with Galileo, etc. all come to mind.
We really have not exceeded the achievements of the Jewish nuclear scientists of the mid to late 20th Century again at any point.
So there is no reason for thinking intelligence grows with time.