When the time comes, I think Mozilla should move on from the Firefox brand to an exciting new browser brand. Mozilla forked Phoenix from SeaMonkey. Microsoft forked Edge from IE.
When or if Mozilla can start merging the Servo engine or Electrolysis multi-process support into Firefox might be a good time. (I like the name Servo for the whole browser. :-) Like IE, Firefox has had a hard time shaking its old reputation (e.g., memory leaks and add-on breakage). A new brand says "this is something new; give us a try again."
I was thinking of having the two browsers coexist for a while now. Firefox for those who need XUL add-on support, the new Servo-based browser for those who don't.
When or if Mozilla can start merging the Servo engine or Electrolysis multi-process support into Firefox might be a good time. (I like the name Servo for the whole browser. :-) Like IE, Firefox has had a hard time shaking its old reputation (e.g., memory leaks and add-on breakage). A new brand says "this is something new; give us a try again."