NCSoft revealed the Gunslinger will be the 10th class in Blade & Soul during the G-Star 2016 convention in South Korea. This class will be introduced in the December 14, 2016 update. However, the update is only planned for the Korean version of the game.
Furthermore Blade & Soul will be going free to play in December, replacing the subscription. An increased level cap, new story quests, locations, and abilities are all expected to come with the update. You can view a trailer for the gunslinger class below: