Guild Wars 2's Heart of Thorns is an Expansion
At PAX South 2015, ArenaNet announced that Guild Wars 2's Heart of Thorns is an expansion set "deep into the heart of the Maguuma jungle" and will not raise the level cap. No more grinding for those extra five levels! The expansion will also introduce new group challenges and new profession specializations, as well as account "masteries" for character progression throughout the new territories.
Along with all these new perks, there is going to an influx of new legendary weapons and precursors, as well as epic quests that help players acquire their precursors.
One new class is coming to Guild Wars 2: the Revenant. It's a heavy-armor class that utilizes the spirits of the mist and famous characters from the lore of Guild Wars. Each existing class will receive new mechanics and weapons that change how their class is played. For example, Rangers can now become Druids and so on.
Another highlight of this expansion is the fact that there will be a new GvG mode called Stronghold based around assaulting or defending a stronghold, and it incorporates a guild team feature in some way. There's a new Borderlands map for World vs. World battles, and there are new Guild Halls for guilds to claim and redecorate.
There is no release date yet, but here is the annoucement trailer.