Now it's official, Firefox OS moves into the „Tier 3“ support category.
Tier-3 platforms have a maintainer or community which attempt to keep the platform working. These platforms may or may not work at any time, and often have little test coverage.
Quote from MDN — Supported build targets
… So this basically means there won't be any extended effort to make Firefox OS more stable, or to make it even more user friendly. Also, there won't be any new advertisements to get a wider user base.