Just thought I'd remind you that there are currently 0 Rust jobs on Indeed.co.uk by title for the whole of the UK. The HN bubble is not how the world at large operates.
Firefox is not the kind of app to drive adoption of the language (like Rails or Python scientific libs etc). It's just an app, people using it could not care less what it's written in.
Go has a bit of a niche, and Rust is trying real hard, but they aren't Javascript or Java, or C#, or Python, or Rails, or PHP, or C++, or Objective-C or... Out in the wider world, they are very much playing catchup, and have a very far way to go.