What is the unacceptable tradeoff of rust?
I'm optimistic about Rust, and it taken great strides to replace C, but there are still many hurdles that prevent it replacing C in microcontrollers and SoCs. Even if it wasn't for the lack of a platform SDK and porting existing code, the risk is too great with lack of official support for many commercial SoCs.
ARM cortex, riscv and espresif all seem like they have first class support. Unless you are talking about peripherals in which case, why would you expect the language to write/maintain low level drivers?
The hurdles to replace it in micros might be worth it depending on the team size and requirements. Personally, I wouldn't expect it to ever replace existing code bases, but could be a reasonable choice for greenfield designs.