Hitman: Absolution will feature an asynchronous multiplayer mode known as "Contracts," IO Interactive revealed at a Gamescom event. Players make their own scenarios, targeting any three characters on a given level with any weapons, and challenging other players to complete the contract in less time (and for more money).
adds a bit of replayability
I doubt this will impact single player at all; it sounds like we'll just have the ability to pick apart the objectives of their pre-established levels (likely requiring players to unlock the levels in advance).