To celebrate the 2-year anniversary of Diablo 3 being released, Blizzard gave every player in the game a buff which doubled Legendary Drops for what was supposed to be a limited time only. Today they announced that since the response was so favourable, they would be retaining that enhanced drop rate as their new baseline rate even when the buff expires.
From the forums:
I come bearing exciting news. Due to the overwhelming popularity of our Anniversary buff we have decided to keep the increased Legendary drop rate once the Anniversary celebration ends. Once the buff is disabled tomorrow morning, you will find that the new base line drop rates for Legendary items will be the same as those you have all enjoyed for the last week.
Happy hunting and link the loot!