Earlier today, ArenaNet hosted a live-stream previewing the new explorable dungeon path for Twilight Arbor, Twilight Assault. It should be noted that this is in fact a replacement dungeon path, not an outright addition. The existing "forward/up" path will be leaving the line-up to allow room for Twilight Assault. For more information about Twilight Assault and the rest of the October 1st build, be sure to check back tomorrow for the official update notes.
Also, the Guild Wars 2 Facebook page has just announced that new hairstyles will also be available tomorrow, though the exact method of acquisition is currently unknown.