Two of Diablo III's most contentious features, the Real Money Auction House, and the more innocuous sounding in-game gold Auction House, will be cease operation on March 18, 2014.
The Diablo team has justified the move by stating that the ease in which players were able to get the most desirable of loot through the auction houses undermined the core mechanics of the Diablo III experience and its reward loop. In addition, the development team has said that the upcoming Loot 2.0 system has been tailor made to exist in a game play setting without the auction houses.
The announcement is likely in preparation for the release of Diablo III: Reaper of Souls, slated for 2014. If this is the case, then we can draw from the March shut-down date that Reaper of Souls may come shortly after.