Now that I think of it, I believe we can expect the boom/bust phenomenon to be evident to an extent.
For example, just on this site, how many new users joined just because of the lockdowns in 2020, versus how many are still actually active now? Of course for bonsai the cycle could be measured in decades where other hobbies and practices it could be measured in months.
I think we're on the boom end of the cycle right now, and may reach market saturation as soon as 2030, at least here in the states. After that we'll see bonsai as a universally recognized practice, but actual activity will decline steadily and substantially, at which point we'd notice that the vast majority of trees are mediocre at best, and the online forums etc. are the hobbyists and competitors while 50% to 70% of trees are the equivalent of houseplants.
We could look to Japan as an indicator of things to come. As they industrialized in the 19th century, and socioeconomic stratification minimized with quality tools and more time becoming available as a result, bonsai exploded until WWII when military expansion took those people and tools away from their trees.
In the post-WWII era, however, we saw the expected mini boom during reconstruction, but never to the same level. Japan being a highly competitive culture, as the bar raised in bonsai fewer people feel it a worthwhile pursuit, and it's now on the decline.
It'll interesting to see how their continued cultural evolution proceeds in this respect.
Still, in Japan bonsai is still widely known and practiced, but on the houseplant level.
My point is, I think we can look for a similar phenomenon worldwide. Globalization will place bonsai on the general upswing for as much as another half century, at which point there will be somewhat of a market correction before plateauing into a relatively stead state.
My youngest daughter's bonsai will be nothing to brag about because they'll be mundane.