If you have followed the news about Firefox -- hopefully by reading yours truly blog -- you know that the past 18 or so months saw some dramatic announcements and changes.
If you group those changes -- planned, in development or on a to-do list -- you come up with two major groups: introduction of features that change Firefox fundamentally, and the removal of features that impact part of the browser's user base.
Features like add-on signing, multi-process Firefox, support for WebExtensions, focus on 64-bit on Windows, and system add-ons, fall into the first group.
You find complete themes, changes to the add-on system and compatibility, removal of NPAPI plugin support, and removal of smaller features such as Hello or the Social API.
Much of it is still an ongoing process, and this article tries to shed some light on the process. It needs to be noted that things may get delayed along the way.