Servo's WebRender sub-project has amazing performance (GPU accelerated compositing and rendering), and is scheduled to be merged in Firefox as fast as possible.

Stylo (Servo's style subsystem) has already landed in Firefox behind a preference flag (not everything is wired at this point), and it also improves perf.

So, yes Servo is of paramount importance for Mozilla's future, because it does make a difference to end users.

Another advantage of Rust is that it allows devs to avoid a whole range of bugs making it easier for them to iterate and ship updates without introducing new tricky bugs (race conditions can be hard to debug).

While dynamic languages may be nice when you want to explore a problem space, the stronger/most static type system is a benefit for upgrading large, mature code bases...