The first piece of info on the upcoming v1.0.5 patch has been released by Blizzard.
Defensive Skill Changes
In our eternal quest to promote build diversity; we’ll be making changes to defensive skills across the board while simultaneously reducing incoming damage. The net result is a survivability buff for players, and an increase in build options as defensive abilities become less “mandatory.”
New Event: Infernal Machine
The Infernal Machine is a device that will allow level-60 players to battle “uber” versions of some of Sanctuary’s most nefarious bosses. While the rewards for defeating these bosses will be great, some assembly is required.
New System: Monster Power
Similar to the “Players 8” command in Diablo II, the Monster Power system is designed to give players more control over how challenging enemies are in each difficulty.
Update: As many of you guys have pointed out in comments, two of these changes are very D2 in flavor, with the Infernal Machine sounding much like the Diablo 2 Pandemonium Event. Check the DiabloWiki.net article for full details on that end game quest, which was added in the v1.11 patch. It required farming certain bosses for special keys, which could then open 3 portals to special areas, where 3 more special ingredients could be obtained, which then were cubed into a portal to Uber Tristram, where the biggest battle and ultimate reward was found.