The GW2 rumored expansion is yet to be confirmed though.
Guild Wars 2 developer AreaNet and publisher NCSoft filed for trademarks just recently, which is said to be for the rumored, and long awaited expansion of Guild Wars 2. The trademark name, complete with the logo, titled Heart of Thorns, was dug up by fans and initially posted and discussed on reddit.
Screenshots taken directly from the United States Patent and Trademark Office shows that the trademark was filed back in January 8, 2015 and is currently Live in status.
Of whether this is the long awaited expansion or not, GW2 fans are still waiting for any official announcement or statement from AreaNet and NCSoft.