Outside of C/C++ and Rust (seeing that MicroPython is irrelevant, as per your comment), what other options will be viable going into the future?
At the moment I don't see any viable alternatives. Rust has a good sized community AND people have been working on embedded use of it for many years already. It took a lot of work to get there. For an alternative to be viable it would have to achieve at least what Rust has achieved so far.
What will ultimately determine if Rust becomes the new go-to language for embedded programming is the community forming around embedded Rust projects.
Ruby is a good example of the power of a community trying to solve a given problem. I think Ruby would not have made it if it were not for Rails. Ruby started out as an interesting language with an atrociously bad runtime and ratty standard library. Yet it Rails had a community that vastly outperformed the qualities of the language/runtime it was based on.
Perhaps embedded programming is where Rust will ultimately make such a huge difference the application of Rust becomes greater than Rust itself. Perhaps a Rust based RTOS, and a sensible approach to how embedded software is structured, modularized, and designed may be the thing that becomes greater than the language itself?
Rust is a great (possibly best) way to build wasm. Wasm is extremely powerful.
Name one language to do both secure blockchain smart contracts, & device drivers, and embedded systems.
And it can use pyo3/maturing to expose code to python. Many significant python libraries are rewriting into rust. Clang/llvm targets means that rust can go anywhere C or C++ can go, including very esoteric systems.
I don't think the jury is out, it just doesn't have mainstream corporate penetration yet, it may never have that and that's fine.
Rust community can/will write bindings to anything, there is no need for other options, people don't realise how powerful rusts polyglot approach is.