Rust isn't really OOP like C#, Java or C++ - it has structs with functions that you could consider an "object" but there is no inheritance. Instead Rust uses traits which are a little bit like interfaces in some languages.

The way the kernel is using Rust at the moment is to produce safe bindings for modules to be written in Rust, i.e. you can create a module in Rust source which will be correctly loaded up, the code is safe by default and will have access to kernel services via bindings. I expect over time that more of the kernel will become Rust, but the biggest impediment right now is Rust relies on LLVM and LLVM only supports a subset of targets that a kernel could potentially support with another compiler like gcc.