> While work at Mozilla on Firefox OS has ceased, we very much need to continue to evolve the underlying code that comprises Gecko, our web platform engine, as part of the ongoing development of Firefox.
So, according to the history of past announcements, if I translate from Mozilla speak to normal English, Gecko will be abandoned in March 2017.
I don't think Servo is mature enough yet.
However, WebKit and Chromium are. They are already experimenting on an Electron based browser called Tolfino and on iOS Firefox is built using the WebView.
1) Tofino (which has now ended) was just an experimental testbed for trying some new browser concepts. It was easier for them to use Electron than to contend with Gecko's ossified embedding APIs. Hopefully positron (https://github.com/mozilla/positron) will allow us to use Gecko in the future.
2) Firefox iOS uses WebView not by choice, but because of Apple's App Store restrictions.