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.
After the Brandstorm engulfs the free city of Amnoon, the Commander receives a mysterious vision, revealing that an encounter in ancient Elonian ruins might determine the fate of Tyria. The Commander embarks on a search for a secretive order of warriors who guard the way into that ancient city, just as the consequences of past choices come home to roost.

In addition to Guild Wars 2’s signature storytelling, Episode 1 delivers further delights:

New Legendary Focus: A relic shrouded in mystery.
New Fractal - Twilight Oasis: Journey to the past and witness events that shaped Elona.
New Raid - Hall of Chains: An influx of murderous undead relentlessly hunt innocent worshipers of Grenth. Infiltrate the Underworld and join the struggle for control over the fates of the living and the dead.
• A notable and much-asked-for quality of life improvement: A new "keys" category has been added to the account wallet, which contains a currency version of several existing items which are used to unlock caches of treasure. These items can be consumed to convert them into the new currencies. Players can find a full list of the new currencies in the patch notes.

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."