As you might have heard, the world of add-on development is going through some big changes. These changes will make developing add-ons easier than ever, and using add-ons safer and more reliable.
We are working to help developers through these transitions as much as possible, and have aggregated the available information and resources here. This page contains timelines, a calendar, migration paths for affected developers, and a survey you can use to tell us which WebExtensions APIs you need. We are also working on a lookup tool you can use to check if your add-on is affected.
We will add more information as we learn of them, and we’re available here in the forums and irc.mozilla.org in the #addons channel to answer questions and provide help.
https://blog.mozilla.org/addons/2016/03/10/developer-support-for-changes-in-add-on-development/