There may be a lot of components and interests involved in this change. As a user of, not developer for, Firefox with its extensions, it's this simple for me:

There may be a lot of components and interests involved in this change. As a user of, not developer for, Firefox with its extensions, it's this simple for me: The day my existing extensions stop working -- the day neither they nor an alternative under the new paradigm offer equivalent functionality -- is the day I no longer have any reason to stay with Firefox. I'm not saying, "Stop, wait, a user is unhappy!" I'm simply saying that, as a perhaps sophisticated user with some more advanced functionality, security, and privacy concerns, the set of extensions I currently use is my only compelling reason for using Firefox over Chrome. Well, that and Google/Chrome's current trend towards its own version of Embrace, Extend, Extinguish wrapped within a panopticon. I embrace the browser as the user client. I'm glad to have security issues addressed, but I also require that the browser do what I want, and not what -- a la Chrome, for example -- media interests want to dictate. I'm watching 2017 with trepidation, and wonder whether and when something may fork. Not unrealistically, though; I'm skeptical any fork is going to have the resources and commitment to maintain a modern, full-featured browser in the face of current and future... err, developments. Maybe such a fork will, both of desire and of necessity, look instead towards a bit of minimalism. Not doing "everything", but doing core functionality well and securely. I guess then we'd have to see whether the content farms with their Javascript++, DRM delivered content, end up leaving such a fork too much out in the cold for it to maintain sufficient interest and/or usefulness to keep itself going.