ArenaNet is going to be down two staff members in the very near future. Community Team Leader Martin Kerstein and UI Lead Kate Welch are both leaving the company; Welch's final day with the developer is September 4th, while Kerstein has apparently already departed. Both of their farewell letters speak highly of the team and give no cause for the departures, and neither yet has any announcements of future plans.
Both Welch and Kerstein have been working on Guild Wars 2 since before its launch. These departures come directly on the heels of the conclusion of the game's second season of living story updates.
[Thanks to Sharvis for the tip!]