There's an official statement from Jolla in 2020 stating that they will improve Rust support. However, I must admit that I can't find anything in the docs.
I know that Whisperfish is working with Jolla to have it distributed via the official store. In my view, this would confirm official support.
I don't know about qt bindings support. I just started an app that uses a Rust library from C++/QML.