Blizzard is adding a new mechanic called "Monster Power" that will make it easier for players to adjust the difficulty of monsters (Increasing health and damage basically) in each difficulty. As far as I understand it, this will only make the game harder if you decide to use the feature.
It's explained in here - http://eu.battle.net/d3/en/blog/6187857/Monster_Power_More_Guts_More_Glory-11_10_2012
1.0.5 will also introduce a new event called "Infernal Machine", which will allow players to fight ubered versions of bosses, and two of them at the same time. Additional stuff is documented here - http://eu.battle.net/d3/en/blog/6120708/Public_Test_Realm_Patch_105_Notes_-01_10_2012
What are your thoughts on this? Does anyone even still play Diablo III? I'm still hoping for a bigger variety regarding levels, but I'm curious to see how exactly will the Infernal Machine change bosses in appearance and what, if any, story will be behind it.