The first details for Deus Ex 3 are slowly starting to trickle out. The 200th issue of PC Zone has Deus Ex 3 gracing the cover. The magazine mentions that a "powerful" and "layered" plot will drive the game.
Eidos Montreal says it's more than aware of fan reaction to controversial second game, Invisible War, and promises mistakes, such as limiting ammo types to just one, won't be repeated.There's a few more details over at CVG.
This said, they are doing their utmost to please newcomers as well as existing fans. Perhaps controversially this time around combat won't be influenced by stats, but will rely purely on your personal marksmanship skills. Instead stats will influence "a vast array of fully upgradeable and customizable weapons", and you'll be able to tailor your arsenal to your play style with mag upgrades, scopes and other add-ons.
What's more, stealth will now rely on a cover system rather than shadows, and damage will be dealt with by a very Call of Duty-style auto-heal. There's probably going to be some debate over those two.
Augmentations have been bumped up and sound fantastic. 20 have been promised for the final game, ranging from 'bungee jump' tentacles that shoot from your back and anchor to a wall when you jump off a building, and the ability to punch through walls to grab enemies in neighboring rooms.