The main focus for this update is to reducethe size of the other patches. After installing this patch it will free up around 800MB of space for those who have already installed Updates 1 & 2. Update 3 should be ready in the next few weeks.
In related news, Guerrilla Cambridge also announced that Update 4 is due in January and is being designed to improve Matching and to help reduce join-game connectivity problems, as well as adding an auto team-rebalancing feature. Update 5 will contain two new free multiplayer maps, plus offline Botzone for Mercenary and Guerrilla Warfare modes. Update 6 will arrive in the first few months of 2014 and will add support for playing Killzone: Mercenary on Vita TV (only applicable to territories where Vita TV is available).