The Halo Council screen captured an advertisement listing the Crimson Map pack as launching on December 10, the Majestic pack on February 25, and the Castle pack on April 1.
The War Games Map Pass is currently available for 2000 MSP and is set to grant access to the three packs, but developer 343 Industries hasn't announced their release dates. We've reached out to Microsoft for clarification on when the map packs are due to deploy.
Update: Microsoft responded to our request for clarification by reiterating the release months for the announced packs and that it had "nothing further to announce at this time." Microsoft stated Crimson is expected in December, Majestic in February and Castle in April.
[Image credit: The Halo Council]