All 3 Rogues in guild prolly already know about the legendary weapon but just in case you didnt here you go.
The new legendaries are two daggers (main hand and offhand) that are only usable by all three Rogue specs. Combat Rogues will be made to use these daggers as well without a DPS loss. The questline will revolve around the pure black dragon (from the egg in the Badlands) and features several Rogue-centric elements.
Melee classes will be getting a buff that is only active in the new raid to help them compete with ranged classes