It's true that a lot of PHP/Python/Go programmers look to Rust rather than C++ when getting into performance-oriented code. But it's not really a stepping stone, because you never have to leave.

It's true that not a lot of people are using Rust for embedded software. That's a much harder nut to crack because so many of the toolchains are proprietary (and embedded support in Rust is still missing quite a few things).