I share the feeling, however I would point out C++23 as the last version, I think the ecosystem will still make it that far, afterwards is as you point out.
Still, look at Fortran, Cobol, C, as examples of 50 - 60 old languages that aren't leaving us anytime soon.
The languages do not die in one day. In 30 years, maybe there are some people writing new code in C++38... and of course the immense code base already existing will stay for decades.
What happens, is there is a steady descent in the number or people using it. I think it has started.
I know even C++ fanboys/lawyers, that are having a lot of trouble to keep up with all features from present and past... And 99% of developers I know, even very good ones, speak of "my 20% C++". So my feeing is 17 is the last version which some people can use 100% of.
Those Turbo C++ tutorials tend to come out of India, and it’s because their schools are stuck teaching that. But those aren’t really tutorials for modern C++, they’re tutorials for C-with-classes at best.
Definitely, however many beginners don't know about it.
Imagine a group of teenager, getting interested into C++ via the Arduino or Pi based school projects, they search YouTube for tutorials (as common practice nowadays) and land on such tutorials.
Still, look at Fortran, Cobol, C, as examples of 50 - 60 old languages that aren't leaving us anytime soon.