In honor of Killzone 3′s first anniversary, the online component multiplayer is being released as a standalone download on PSN today. It includes access to all game modes such as Warzone, Guerilla Warfare, and Operations, as well as the original Killzone 3 maps/DLC maps. So keep in mind, you will be able to play all the modes and maps all up until you reach the rank of Seargant I.
For anybody who already owns Killzone 3, you might be glad to know you will be getting a Double XP weekend starting Friday, March 2 at 8:00am Pacific time which will go on until Monday, March 5th. For those of you using the trial multiplayer, this will have no effect on since you probably would want to adjust to the experience first before you reach the max rank you can get to.