The average speed of the winner of the Tour de France in the year 1903 when it was founded was 26 kph (16 mph). The average speed of the winner of the Tour de France from the year I was born was about 35 kph (22 mph) and in 2021 Tadej Pogačar's average winning speed was 42 kph (26 mph). The steady increase of the speed of the race is because of advances in the conditioning of the riders and advances in bicycle technologies and materials. In cycling, the weight of the bike is a huge deal. Today's pro-level bikes are made out of carbon fiber and titanium, with disk brakes, electronic shifting, electronic data display, and they are remarkably areodynamic. The riders are incredibly fit now, and before the 1965 substance ban, the competitors used any substance to enhance performance, and now they can't do that.

There is no reason to believe that speed won't continue to rise for the same reasons of techology and fitness, the advances will just be slower because it will be harder to go faster only using human power, but they are going to happen. I remember seeing my first e-bike about twenty years ago at a trade show. It was $14k and was made by Honda and now a good one is a grand, so the inovation is continuing.