The expansion features a lot of new content. There will be New Large Scale Content as well as new Dungeons. Soulstone Plains will serve as a new PVP zone. Lastly, there will be a new capital city: "the palatial and expansive mountain city of Zaiwei will serve as your new base of operations, activity hub, crafting workshop, and social center. Its broad thoroughfares and gold-leafed monuments are matched only by the city’s plights, and need for assistance from willing warriors."
Use this link if you want to know more details about the upcoming expansion.