> most of the recent improvements to Firefox were initially prototyped and developed in the experimental Servo engine which was to my knowledge intended to eventually replace all of gecko. Most of the team for that has been let go.
This is not the case. Servo worked on big experimental moonshot projects. They had some major successes (Stylo, WebRender), but the rest of the Firefox team wasn't sitting around twiddling their thumbs. I don't think Servo ever made up more than a small fraction of the overall Firefox workforce. They had to pick and choose their projects. Note, for example, that Servo embeds SpiderMonkey instead of writing its own JS engine from scratch: https://github.com/servo/rust-mozjs
Don't worry! SpiderMonkey still has additional cool projects coming down the pipeline, none of which are dependent on Servo.