Externally, Firefox has become a brand. Servo is comparable to Gecko or WebKit (it is a browser <i>engine</i>), although it is new, not finished, and uses novel techniques.<p>What follows is speculation on my part. I am not a Mozilla employee.<p>Mozilla might, in about five years, offer a new product for desktops which features Servo, SpiderMonkey (the JS engine currently used in Firefox), and an as-of-yet undefined chrome (the UI bits around the rendered page). It may be a mobile product instead, or a product for a different type of hardware, although the current thinking seems to be to target it for desktops.<p>Whatever that product is, it may still be called Firefox or a derivation of that brand (as Firefox OS was), although it might have a completely new name (it worked for Microsoft Edge, after all).<p>(Updated for clarity.)