According to the German Xbox 360 Dashboard leak reported by MP1st, first DLC Map pack for Halo 4 will be released in two weeks of time from now. According to the leak, there will be three Map packs that will come in December, February and April.
Crimson Map Pack is due December 10th, Majestic Map Pack due on February 25th and then Castle Map Pack will appear on April 1st 2013.
Halo 4 War Games Season Pass will allow users to download all the above DLC with a discounted one time payment of 2000 Microsoft Points. Till now, there is no official confirmation from Microsoft regarding this DLC for Halo 4.