I maintain a couple XUL addons that work with Zotero. Zotero has been distributed as a Firefox addon and a standalone XULRunner application, so my addons are listed on addons.mozilla.org. The next version of Zotero will drop support for Firefox, but I anticipate that the standalone version will probably continue to be supported past November 2017 when support for XUL addons is dropped.
What are my options for providing a smooth transition for users of my addons? I assume there is no way to publish an update that changes the updateURL to something other than addons.mozilla.org. The next thing I can think of is to publish an update that displays a warning to the user that no more updates will be posted to addons.mozilla.org and that the user should uninstall the addon and reinstall it from my site (and that version I guess would need a different addon id). Is there anything else I can do?