I mean, I guess deus ex aliens is always possible but you just have to ignore it to make any reasonable predictions about the future. I think the three factors affecting innovation are mode of production, demographics, and what's left to discover. More people means more brains to develop technology of course. Socialism and communism means a more efficient use of resources. People talk about a demographic crisis facing China, but they over-exaggerate. Assuming China fails to reverse this, it's still not as bad as some think. The advanced capitalist countries have 1-3% of their workers employed in agriculture, whereas China has ~17%, or about 134 million farmers (they would only need around 24 million or less at 3%). Also something like 40% of college graduates in China are STEM, whereas in America it's 20% or under (obviously mobilizing your graduates properly matters too, but idk how to quantify that). So China's population can shrink for the next few decades while still growing its highly educated workforce. Even if they hypothetically reach parity with America, China's economic model is superior so they'll still be inventing things faster I think.

So the real limit to the rate of discovery, innovation, technological change, whatever, would be running out of things to discover. There is still a lot left to invent. Let's look at aerospace. The author laments the fact that passenger airplanes are basically the same as they were in the 1960s. Indeed, airplanes (and airships...) were cutting edge technology in the first decades of the 20th century, and there were lots of experiments on passenger airplanes after that (RIP flying boats). The modern form factor did it the best, so we've stuck with that, and every new plane just tinkers around with the materials, engines, wings, etc. a little bit. There's also the issue that aerospace is really expensive - new passenger planes take billions of dollars and a couple decades of development. Ekranoplan air freight, flying-wing passenger planes, and clean jet fuels could be the next big improvement, but they'd take decades and hundreds of billions of dollars to actually reach the same level of ubiquity as the classic passenger airplanes enjoy now. Who is going to develop that? Boeing? Airbus? Yeah right. And China's airplane industry is really young in comparison, so you can't count on them. The next big change in aviation won't be here for a while. However, now the space part of aerospace is booming like the airplanes were a century ago. Rockets were cutting edge in the 50s and 60s, but now in the 20s you see tons of countries and companies (mostly the US and China) developing their own rockets. Once rockets go through the same thing as airplanes did, it'll be space tugs in the 22nd century or something... So yeah, there's a lot of room for technological development still and I don't think we'll hit a wall anytime soon.