MoP's release date was announced on July 25th and released on September 25th.
Cata's release date was announced on October 4th and released on December 7th.
WoTLK's release date was announced on September 15th and released on November 13th.
WoD won't be out until late October / November. It might even take until December 20th, with all the development setbacks Blizzard has encountered so far.