Yeah, there's progress on 8-bit and 16-bit support. We're tracking our work on improving Rust for embedded systems in this roadmap issue [1], with details in this RFC repo [2]. As part of that, we have preliminary support for the 16 bit cpu MSP430 in-tree [3], and a fork for the 8-bit AVR in [4].
[1]: https://github.com/rust-lang/rust-roadmap/issues/15
[2]: https://github.com/rust-embedded/rfcs
[3]: https://github.com/rust-embedded/rfcs/issues/20
[4]: https://github.com/avr-rust/rust