If I check for update in FF 39.03 it says FF is up to date. Mozilla.org shows no FF 40.0 stable. But Snapfiles and Softpedia do. It gets weirder all the time.
Edit: Just checked Mozilla again. Now it has 40.0 for download. How can they get beat at their own game? Seems pretty strange. Check for update is still 40.0 unaware.