No, I still need the old Plugins and Extensions to work so I switched to Firefox ESR 52.5.2 (64 Bit) and Still use SeaMonkey 2.49.1 - Either of which STILL Use the Old Plugins.
When Firefox no longer supports the old Extensions I'll be using SeaMonkey alone: SeaMonkey STILL Supports FEBE
https://addons.mozilla.org/en-US/firefox/addon/febe/ NOW and likely will support it for a long time to come.