I have a feeling that after all the uncertainty and turbulence and vociferous discussion that everything is going to work out fine in the end. Yes, Firefox is going to abandon us. No, we are not going to be terminated. We and many other add-ons that depend on the presence of FF's XUL and XPCOM components (now removed from 45.0) will continue to be supported by FF forks such as Pale Moon and others. I get the feeling PM was launched when some developers got fed up with FF bloating its features and junking it out, and decided to fork and develop a clean, faster, lean and mean browser which became Pale Moon.
In the end I can only wonder of FF's runaway development will ultimately end up in their losing user base to the other browsers developed as FF forks. I don't understand their monthly release cycle, stamping out a new FF whether or not it is needed. Bug and security fixes, yes, but I think there are enough people like me who believe FF already has enough features and that new features should be rolled out as an infrequent occurrence, and only when it's a very attractive feature. I don't like my computer or its software morphing on a daily or monthly basis. I'm happy right now with everything it does and all I really want is bug fixes and security patches. In a way maybe Firefox is doing all of us a favor by driving us to Firefox based browsers that don't have a bunch of hyperactive, OCD kids driving their development.