Initial dx11 beta in game update notes: "The goals for the initial implementation of DirectX 11 are stability, visual, and performance parity with DirectX 9. Most players will likely see negligible performance improvements at this time."
Meaning: "...integrate the open source rendering library bgfx into Guild Wars 2."
When Anet is done they will have a great technical base to deliver for every platform (see: render backends; supported platforms).
The next step would be Vulkan (this comes with MoltenVK - so we have a new Mac-client). And bgfx opens the path to consoles and mobile devices. Visual improvements will be done on the way.
And maybe they remaster Guild Wars 1 with the new engine. That would be awesome.