Sony and EA have come to an agreement to bring Battlefield 3's DLC to the Playstation 3 first. Considering that Microsoft has had first dibs on the DLC for the Call of Duty DLC. The wait for the map packs or DLC won't take a month or more for it to surface on 360 though, the agreement that they've made is that the DLC will come to the 360 a week later. The first DLC to hit will be the "Back to Karkand" package which will include four maps from Battlefield 2 all remade with the Frostbite 2 engine. Expect Battlefield 3 out later this year, and the DLC a little later.
