Rust

Rust

Subsequent Fortran releases are more or less backward-compatible, and recent ones even support pointers and recursion, but how many places are they used?

In more places then you expect. I know few people who thought like you do till they actually participated in bioresearch, weather prediction research and so on. They found out to their sudden surprise that new projects are still written in Fortran. Usually it's a mix: IT guys write the supplemental logic in C/C++ and non-IT scientists write their algorithms in Fortran. In that sense Fortran is still alive. Number one request for Exacycle is Fortran support (perhaps they already implemented Fortran support at this stage? I don't know).

People using C++ now will continue using it, but in maybe ten years new organizations and projects that need C++'s power will begin to pick up Rust (or something) instead. Second-tier languages will come and go, and be used for the easy problems, as always.

And Rust in one of these second-tier languages. The same happens with other industries, too. Think track gauges or QWERTY keyboard: once upon time it was easy to change track gauges or layout of keyboard but by now it's basically impossible. You can change some auxiliary pieces (railroad ties are made today from stone, wood, plastic or even fiberglass) and specialized cases use specialized gauges or keyboards, but mainstream is stuck.

My point is that Rust is the first language above the horizon that seems physically capable of supplanting C++ on problems where, before, nothing else could even be seriously considered.

Nope. Rust is yet-another-pretender with overblown hype.

If it sputters out, the world will continue with C++ as before until the next contender matures.

Well, the next contender will probably be called C++17, so it's not like we'll need to wait too long.