I found many info in this announcement.
As I previously commented, with limited resources we will need to make the tough decisions. If we want more from the dev team, we probably need to think about how can we help to ease the restriction.
This means continuing to build support for add-ons. In order to get the new browser to users as soon as possible—which was necessary to iterate quickly on user feedback and limit resources needed to maintain two different Firefox for Android applications—we made some tough decisions about our minimum criteria for launch. We looked at add-on usage on Android, and made the decision to start by building support for add-ons in the Recommended Extensions program that were commonly installed by our mobile users. Enabling a small number of extensions in the initial rollout also enabled us to ensure a good first experience with add-ons in the new browser that are both mobile-friendly and security-reviewed.
More Recommended Extensions will be enabled on release in the coming weeks as they are tested and optimized. We are also working on enabling support for persistent loading of all extensions listed on addons.mozilla.org (AMO) on Firefox for Android Nightly. This should make it easier for mobile developers to test for compatibility, and for interested users to access add-ons that are not yet available on release. You can follow our progress by subscribing to this issue. We expect to have this enabled later this month.
Our plans for add-on support on release have not been solidified beyond what is outlined above. However, we are continuously working on increasing support, taking into account usage and feedback to ensure we are making the most of our available resources. We will post updates to this blog as plans solidify each quarter.