The official Pokémon facebook page has just revealed Doublade, Honedge’s evolution. Doublade retains the Steel/Ghost-typing and the No Guard ability. Nothing else is known at this moment but the official website should be updated soon so we will probably get some more information about it.
Details about Doublade have been added on the official site. It can learn the move Sacred Sword, a move that was previously exclusive to the musketeer trio and Keldeo.