Per the website "The Examiner", SWAT will be added next week (sorry about the text/font and its background. Copied and pasted from the article):
Halo 4 for the Xbox 360 was only released just this week and 343 Industries announced Friday a playlist update coming next week.
While Halo: Reach enjoyed monthly playlist updates, 343 Industries plans weekly updates for Halo 4.
"We will maintain a static set of playlists and feature one or two “rotational” playlists on top of that," community manager Jessica Shea wrote on Halo Waypoint. "We will be monitoring trends and statistics closely so we can react accordingly to your preferences and likes. For instance, if one of our rotational playlists consistently holds a higher population than one of our static playlists, we will consider swapping them out based on player demand. The process will be fluid and based on numbers, and we’re extremely excited about the benefits of our new approach."
So what is coming with the first playlist update? SWAT with some changes to both weapon damage and the HUD. Players will be equipped with Battle Rifles, DMRs and Magnums, have no shield or radar tracking, and will not be able to use ordnance drops in this game mode.
Here is how 343 Industries tweaked the three weapons for SWAT.
DMR – 3 bullets to the chest, 1 bullet to the head
Magnum – 3 bullets to the chest, 1 bullet to the head
BR – 7 bullets to the chest (this gun shoots three bullets in a burst, so the first bullet of the third burst will kill the player), 1 bullet to the head
Here are the maps that will be available in the SWAT playlist.
Haven
Adrift
Complex
Abandon
Solace