Blizzard Quote [source]

Replayability and ideas like Endless Dungeons come up a lot around the office. We definitely have plans to expand the game in these areas. Adding more monster power levels is also something that we have discussed. I personally love the idea of an endless dungeon, don't take that as a quote that I promised we are adding them though! At the heart of that idea is something really compelling, wave events, endless dungeons, hold out missions etc. Standing as the lone hero, or one of a party of heroes, against an onslaught of demons really sells the fantasy of Diablo, it's just a matter of taking the seed of that idea and iterating on it to a point where it feels like it fits into the game as a piece and not just "the only thing to do". I do hope that down the road we can find some way to make that idea a part of the content options players have at their disposal. I've said one numerous occasions, in a perfect world, when a player sits down at their computer for the evening to play the Diablo the question I want them to say to themselves is "What do I feel like doing tonight?" not "Ok time to run Act 3 again".