Firefox 57 is expected to be "officially" released tomorrow, 11/14 --- Major Geeks has already "pre-released" a copy of the (allegedly) "final" version.
If I understand things correctly, all LEGACY add-ons will no longer work... they will be automatically disabled, perhaps even completely removed. I also believe that there will be no "tweak" to override this situation.
So be very careful tomorrow (or afterwards) if/when you decide to "upgrade".
I know that on some of my systems, an (older) version of WOT is all that's keeping FF functioning... I can't explain why... all I know is that, without this (older) WOT, FF is worthless to me on those systems :-(