Two new features being added to the PC game are co-op play and air dropped vehicles. Co-op play will allow you to play through the single-player levels over the internet or LAN with the aid of human players and bots. There will also be some customisation options allowing the player to change how the bots in the game behave.
Air dropped vehicles will give players the ability to request for a vehicle to be dropped at their location, when they need it the most. The update will also have a load of new bug fixes and gameplay tweaks which you can read about over on the game's official website.