https://blog.mozilla.org/futurereleases/2019/06/27/reinventi... says they were planning in June to have a "feature-rich, polished" fennec release "this fall".
https://github.com/mozilla-mobile/fenix/issues/879 "[Meta] Fennec -> Fenix Transition" appears to say the transition will happen in Q4 2019.
The Android releases of fennec used to be updated for each Firefox release, but moved to ESR with the most recent ESR release. I think that means that since then nobody has been keeping the Android port working as changes come in (but ESRs are supported for a year or more, so maybe I'm wrong to think that the date of the next ESR release is relevant).
https://github.com/mozilla-mobile/fenix/issues/574
is about web-extension support; the recent updates say:
« Product is looking into feasibility »
« Tentatively adding needs:gv label until we know what additional GV work will be needed to support general purpose extensions. »
The issue is labelled 'Feature:FennecTransition' and 'feature request'. It isn't labelled 'should', and some other 'Feature:FennecTransition' issues are.
It isn't clear to me whether they're planning to release a new version of "Firefox" on Google Play that uses the fenix codebase, or release fenix as a separate app and declare that the fennec one is obsolete.
https://github.com/mozilla-mobile/fenix/issues/879 and
https://github.com/mozilla-mobile/fenix/issues/934
have some interesting hints, but I can't tell what they've decided.