Exculding those that have been reaveled in the trailer...
-intelligent AI damage system(when you shot someone in the knees they cant walk bullet holes in people and on you like in hitman)
-better stealth missions
-more interactive with ai
-more place to go inside
-create your own gang customize your guns
-killing random people has more effect then just stores
-a legit hot coffee-esqe part
-be able to travel
-not only to take place in new york
-just more all around interactivity