Mozilla today published the extension roadmap for Firefox, which reveals a huge shift with extensions in the browser. With the release of Firefox 57, support for all classic XUL extensions will be discontinued.
Firefox 57 is expected to be released in November 2017. The release will feature the switch to WebExtensions instead of XUL add-ons. Additionally, the special compatibility layer which exists currently for add-ons having issues with the multiprocess (e10s) mode will also be removed from the browser.
Firefox 53, which should be released on April 18, 2017 will have the multiprocess mode enabled by default for all users. If an installed add-on has the flag multiprocessCompatible=false, Firefox will continue running in the single process mode. The browser has a special blacklist of add-ons which have issues with multiprocess mode. If an addon is in the list and does not have the mentioned flag set, it will be disabled.
In Firefox 53, add-ons will only be able to load binaries using the Native Messaging API.
Finally, starting with Firefox 53, it won't be possible to submit any new classic add-ons to the addons.mozilla.org (AMO) repository.
Firefox 54 to Firefox 56 will have multiple content processes and sandboxing. This is different from the single content process currently being used.
Starting with Firefox 57, the browser will only run WebExtensions. By that time, AMO will still host classic extensions and allow their authors to update them, but this won't be for long. The exact cut-off time for their support hasn't been determined yet. (via Mozilla).
Developers have less than a year to port their add-ons to WebExtensions APIs. The unacceptable thing about this transition is that WebExtensions are limited and not as powerful as the XUL framework.
Some users have an opinion that Mozilla is digging the grave for Firefox by discontinuing support for all the great extensions which made it such a popular browser. Once XUL support is killed, the browser won't be much different from Google Chrome except for the rendering engine. The rendering engine of Firefox is slower that Google Chrome's Blink engine. So, these radical moves can really change the market share for Firefox. Many users have already decided to switch to Vivaldi, Google Chrome or Opera.
What about you? Is this change in Mozilla Firefox acceptable to you?