APNG was largely ignored on the web but this may not be the case soon as Chrome/Chromium is targeting to support APNG in
My wild speculation / my hope to Chromium supporting APNG is that Google may need APNG for displaying animated stickers in (future) web client for Allo, Google's messaging app. Of course I don't know whether Allo is actually using APNG for its stickers, but iMessage and LINE are using APNG.
I don't think my concern worth a bug report in Bugzilla. Where can I get relevant news/info about APNG implementation in Firefox besides bug 257197?