The first episode of the fourth Living World season for Guild Wars 2 came out just a short time ago today from ArenaNet. This new content is free to everyone that owns Guild Wars 2: Path of Fire. You're looking at new story content, a new Fractal, a new Raid, and more.
New Legendary Focus:New Fractal - Twilight Oasis:New Raid - Hall of Chains:

Remember if you miss out on logging into the game when the first episode is available, you miss out on getting the first episode added for free. Same deal for the subsequent episodes. So yeah, avoid having to pay later on by logging on now. New episodes usually come along every "2-3 months."