That was the original idea, until they fired most of the developers that eventually found a job at Apple, Amazon, Oxide, Microsoft, Google, Ferrous Systems...
They are now driving where Rust goes, and it isn't in Firefox which has stop rewriting stuff and now adopted WebAssembly sandboxing instead.
To be more specific, less than 10% of Firefox is written in rust, according to their lines of code stats. Looking at how Servo was put out to pasture, I dont know how much that will grow under Mozilla's stewardship?
