I wonder if after Mozilla writes Servo in Rust 1.x and Google sees how fast Servo is, even compared to its own JS engine, it will also consider writing a new JS

I wonder if after Mozilla writes Servo in Rust 1.x and Google sees how fast Servo is, even compared to its own JS engine, it will also consider writing a new JS engine in Rust 2.x (I assume, by then), as I doubt they'd use Go for that. Same for the whole browsers. Due to the safety features of Rust over C++ we might see both Firefox and Chrome be rewritten in Rust over the next 5 years.