ArenaNet are inviting all pre-purchases of Heart Of Thorns to a new testing weekend, to give Stronghold and the revenant a run their money. 

 We’re inviting all pre-purchasers to join us for a special revenant test weekend starting Friday, July 10, at noon Pacific Time (UTC-7) and running until noon Pacific Time (UTC-7) on Monday, July 13. During this test weekend, you can create and play a revenant beta character anywhere in the existing game: PvE, PvP, and WvW! We’ll also be opening up our new Player vs. Player game mode, Stronghold, to all players who play in the queue for Unranked PvP over the course of the weekend.

Lasting a whole weekend, it's going to give players the first opportunity to play the Revenant's newest Legend (the Ventari) and you'll also get your hands on the newly revealed Mist Champions. It sounds as though ArenaNet are also going to be all ears when it comes to feedback:

These testing events are an exciting opportunity for you, our players, to help shape the development process and the experience you’ll have when Guild Wars 2: Heart of Thorns™ is completed. Though the trend these days is often more to treat beta events as simply marketing sneak peeks, we very much believe in having beta events that mean much more. We want to let you experience vertical slices of the final game experience; we’re going to listen to your thoughts and suggestions, we’re going to iterate on the experience, and only when we love it will we ship the expansion. These are real beta tests, and you have the real opportunity to help shapeGuild Wars 2: Heart of Thorns with your feedback.

I'll be jumping into the event, so I'll let you know my thoughts on the Ventari and the recent Stronghold changes. You can read the full blog post here.