All significant advances in aircraft were a result of revolutionary advances in power plants. The Wright brothers engine made powered flight possible for the first time. Rotary engines made airplanes militarily useful, radial engines made practical airliners, and jet engines enabled revolutionary increases in performance.
The question is what is the next revolutionary power plant ? Personally think it is going to be electric but what will be the energy source, battery, hybrid battery, hydrogen, something else? That is where there is much uncertainty with likely many failed attempts before someone comes up with the secret sauce.
The journey is going to be interesting….