In that case, you can simply not use the dynamic allocation features of Rust, just as you can simply not use malloc() in C.
> GC languages
> Dynamic memory allocation on embedded is the exception
Right, I was referring to Go and Swift with the comment about GC. Since rust didn't have that problem, I mentioned why major adoption might not be forthcoming.
I understand that you can statically allocate all you want in Rust, but it's memory safety, particularly with regards to object ownership is one of its major selling points. Object ownership and lifetimes are trivial when everything is static.
The other arguable selling point to rust is its standard library, but much like C++ the standard library would be left aside in most embedded applications.
So it doesn't buy you much of anything at all, but it takes some work to setup, plus you are fighting the momentum that C/C++ has. Unless there is some other compelling reason to use it, I don't expect much adoption.
A lot of the things rust brings to the table aren't always relevant on embedded platforms. Dynamic memory allocation on embedded is the exception, not the rule. Everything is statically allocated, so memory management is relatively simple -- everything sticks around forever.
The things that make C/C++ good for embedded are sorta what make it unfortunate for general purpose use. The things that make Rust/Go/Swift good for general purpose use make it unfortunate for embedded use.