No, they really haven't. In fact for a good chunk of centuries (from 16th century onwards), the optimism for the eventual future developments was endless. At some point there was a few scholars saying that during the end of 19th century, but still not some widespread belief.
That said, discovery probably also follows an 80/20 rule, and we're somewhat at the tail end now. We haven't had any major new discoveries, of the kind that we had regularly until the 60s-70s, for decades now.
Progressive refinement (like going from the workstation to mobile phones and watches) yes. But nothing like the advent of the computer, the internet, and so on.
And even less earth-shattering stuff than the time before that (which got us from the steam engine and electricity, to nuclear energy, radio and tv, flight, space exploration, the digital computer, QM and relativity, the DNA, and so on). Stuff like that was coming decade after decade up until the 60s-70s. After that, not so much.
>"We might have invented everything" would imply that the space of all possible inventions is bounded, and we're running up against the edges of the box. But I don't see any reason it should be bounded.
While there's some quasi-religious optimism (like the universe owe us endless discoveries forever), there are real limits, and notions like "low hanging fruit" and "marginal returns" do come into play.
Really?
I've read some pretty authoritative writings about how humanity always thinks The End is Near, that we live in an era of decay after a lost Golden Age, that today's youth is a uniquely corrupted lost generation and so on.
Blockchains are one that I would present. I'm sure experts in other fields would have examples from their worlds as well. We just haven't had time yet to appreciate how dramatic some of the discoveries are going to be.
In that regard, the number of inventions (as subset of all sets of configured matter)- is similarly bound. We might argue that such a bounding is infinitely expanding along with the universe, as space is a important variable in the equation. Even so, my assumption is that space becomes irrelevant after a certain point of expansions. (If I have 2 atoms in a field of a billion of square miles, the number of configurations is only trivially changed by adding a few more square miles.
Once more, even if an infinitely expanding universe equates to an infinitely expanding art of inventions (configurations) - the fact remains that the set is fixed for any given time point.
In our cultural spectrum, we constrict our inventions to optimize for "use", but perhaps "use" is too narrow.
If you look at cultural events like Burning Man, you see all sorts of completely useless inventions. Fascinatingly useless inventions.
I actually hope that one day when we do enter post-scarcity that we can stop obsessing so much on whether or not something has the subjective quality of "use", and allow the boundaries of our hyperdimentional invention-space to grow exponentially.
I think "toy-space", or "art-space" if you will, is a logical expansion of "invention-space".
A delightful example of an invention outside of our current culturally accepted bounds of invention-space: https://youtu.be/apVR5Htz0K4
A good parallel can be draw to evolution in painting. Up until the invention of photography, painting evolved to be photo-realistic. It made amazing strides, with breathtaking results. Once photography made that evolution path obsolete, painting struggled to find a new utility function. Out of that struggle, we got amazing outcomes in conveying feelings, a new utility function. Work in the first half of the XX century, from the likes of Munch, Dali, Picasso, optimized this function up to its limits. From then on? Painting is somewhat lost in the solution space without an utility function.
Take a chess game as an example. No one would say there weren't creative inventions regarding tactics and strategies to win, but the bottom line is that the number of possible chess games, no matter how staggeringly huge, is still finite. In the end, no matter how intelligent the players, there will be a point were nothing will be left to be invented, so perhaps life is also a solved game in that respect.
In that case the issue is that some parts of the universe are out of reach from other parts, because of the light-speed limit.
For most areas of innovation, we don't seem to be near the limits. Certainly it is a sphere where today we are seeing more opportunities than completed explorations, but that may cease to be true in 50 or 150 or 1500 years.
I like the "invention wavefront" analogy, but I unfortunately can't remember where I learnt it.
Imagine the high-dimensional space of all possible things that can be invented. In the "centre" of the space is a hypersphere containing everything that has been invented to date. Every new invention is invented by "poking outwards" in one small place on the boundary of this hypersphere (hyperglobule) so that the hyperglobule now contains something that it didn't contain before. All inventions that could possibly be invented right now exist on the surface of the hyperglobule. Think of this as the "invention wavefront". Notice that as the globule expands, the wavefront becomes larger, not smaller. What this means is that as more things get invented, more new inventions become possible (intuitively: you can't invent better brakes for a car until you've invented a car, and so on).
"We might have invented everything" would imply that the space of all possible inventions is bounded, and we're running up against the edges of the box. But I don't see any reason it should be bounded.