No, there are no expansion packs available. However, what there is in the place of an expansion is an ever changing world. The developers have discussed in the past and in recent interviews that there will likely not be any expansions to the game. What you do get in its place is a constantly changing world, powered by their Living Story content. The Living Story is new content that expands upon the original storyline, however, can be played on its own should you wish to do so. The story has major impacts on the current world, new zones open, cities have been destroyed, zones have had terrain incredibly changed by this. It is all very exciting. New rewards, new content all available every two weeks or so. You also get the seasonal content, such as Wintersday, Dragon Festival, and the Halloween content.