Firstly it was just announced that the game will officially launch on June 20th :)

At the same time, the new level 60 content Gauntlgrym will be released, which is an underground dwarven area with PvE and PvP content.
If you want to preview the area here's a video of it, I haven't watched because I wanna be surprised:



Also, the first free content expansion Fury of the Feywild is on track for a Summer release, which chronicles an attempt by Fomorian Giants to seize the Elven city of Sharandar.

Lastly, there are a huge number of updates to be released before June 20th. The basic idea is to make the game more difficult - which I'm personally all for, the game is super easy, especially after you get companions - and further balance the characters and tweak skills. For the full, huge list of the tweaks see here.