Battlefield 3 among other things will also feature a standalone co-op mode with 10 maps for two players. This may be a surprise announcement for many but I think, this is a counter measure against the rival product.
It’s an extra features in an already extensive multiplayer component of the game, which many fans would appreciate. We don’t know any specifics yet, but it is only the matter of time before we start hearing more.
We will update you when we have more information on this.