Inferno and 18 Item Tiers
      

  We have the actual visual progression looks nailed down, so I guess the direct answer is we're not looking to make any more beyond those 18. We're not nailed down on how we're pacing them because we're still creating a decent amount of unique armor pieces, which get more bang for the buck being placed around end-game itemization.  
      

http://www.blizzblues.com/us/inferno-and-18-item-tiers-27830852899.html