But technology have been steadily advancing (possibly exponentially) for hundreds of thousands of years, and there is no reason to expect it to suddenly stop. The problem is that you're looking at the limitation of very specific technologies to draw broad conclusions about entire categories.
The examples you gave about flight and rocketry are the classic cases found in literature about the subject. They are instructive, but also a bit deceptive. If you take "airplanes" as a category, then yes, you can show that they reached an optimal design limit, at which point their progress slowed down considerably. But that is not the best way of looking at the situation. Transportation technologies have been advancing since the dawn of humanity. From the wheel, all the way to modern hypersonic fighter jets. Since the introduction of the plane, humans have figured out how to get into space, going farther and farther each decade. Even if you consider the advancement in airplanes, I'd say wood planes that can travel at running speed to modern Boeing composite Dreamliners are impressive for just 100 years (a blink of an eye compared to the length of human history). Individual technologies do reach a limit, but I don't think technological categories do. At least not in the short term. Like Joe said in response to your post, what if fuel-less rockets were developed? Here is a link to NASA's latest test of a fuel-less system that they tested last year:
https://www.libertariannews.org/wp-...ustProductionFromanRFTestDevice-BradyEtAl.pdf
The news really shook the world of physics when it was released a couple of months ago, and numerous teams are trying to confirm and replicate the results. But that's nothing. History is long. In 1900, the greatest minds couldn't even begin to conceive of the computers we have today. The whole concept would have sounded surreal and impossible to them (despite some attempts at simple mechanical calculating machines).
Now for computers. I design computer chips for a living. The advancements that I've seen in my short career blow my mind. I don't know if Moore's Law will continue at its current pace, but it CERTAINLY will continue at some pace. People have been saying that we've run into the limits of transistor miniaturization for a couple of decades now. But Intel just announced a new fab in Israel to start their next die shrink. They envision continuing with the same silicon die shrinks until early 20s at least. After that, we've truly run into the limits of traditional transistor miniaturization in a single plane. But silicon is far from the only option, and we're WAYS away from the computerization limits imposed by the laws of physics. In my lab, we have computing prototypes that use the spin of individual particles to perform computations (called spintronics). In theory, these can be scaled to create computers that are trillions of times more powerful than anything we have. And even that is not the end of the line. And I'm talking about classical computing. Quantum computing is a whole different game.
I think you're right about the unlikeliness of competition between n A.I. and humans, but I don't think you're completely right about the reasons. For one, energy efficiency is a temporary problem. Eventually, we will have fusion power with inexhaustible fuel. Who knows what else we'll have in the future. Anti-matter power plants? Power extracted it from the vacuum itself? And that's not counting the unimaginable techniques that can be invented by superhuman A.I. The other part about enhancing our own brains is spot on. We will do so as we understand more and more about what intelligence actually is, until we ourselves become the A.I. I believe that is the most likely scenario. But who knows? As our capabilities continue to climb, the power of even a single individual to inflict damage also increases. Hopefully we'll be able to survive the malicious elements in our own species.
