Over two years after Diablo 3's release, Blizzard are still thinking up new ways for its fans to click on things. They describe update 2.1.0 as a "major content patch", and it's designed to further encourage repeatable play—continuing the work started by Reaper of Souls to create a long-lasting ARPG. In a preview post on the Diablo 3 blog , Blizzard detail the major contents of the patch, which they say will be arriving soon on the game's Public Test Realm.
One major new feature is "Seasons", which will operate similarly to Diablo 2's Ladders. Players participating in a Season will start a new character for Level 1, and gain access to new Season-specific achievements (called Conquests), exclusive rewards and unique Legendaries. They'll also get to compete across new leaderboards, that will track their progress across each specific Season.
The other big addition is the Greater Rift—accessed by collecting Greater Rift Keys from a Nephalem Rift's Rift Guardian. Is the word 'rift' starting to lose all meaning to you? Me too.
Greater Rifts are a race against time, in which players must fill a progress bar by killing enemies. Much like Wildstar's questing system, the bigger the enemies you tackle, the quicker the bar will fill up. Successfully complete the Rift and you'll move onto the next, more difficult tier.
Finally, a new area is planned. The Cesspool was originally meant for Reaper of Souls. While it wasn't ready at the time of the expansion's release, Blizzard kept working on it. As of the next patch, you'll have a chance to encounter the "festering, dank underworld" in Nephalem and Greater Rifts.