Does LEDE plan to support RUST language ?
There are no specific plans regarding Rust support at the moment, but there aren't plans to not support it either
I am not sure about the specific requirements for Rust but I do know that we're unable to support Go atm as it is incompatible with musl libc.
Since the Rust compiler is written in Rust, it must be built by a precompiled "snapshot" version of itself (made in an earlier state of development).
and do not support cross-compilation.
For cross compilation, maybe this is helpful.
rust platform support list