343 Industries will be bringing a new Forge World map to Halo 4 on April 11th. Titled "Forge Island," the map will allow players to use the in-game map editor to create something using this island themed map as a base for their creation. It'll also come with new Forge pieces.
There's some gameplay footage of Forge Island above if you're interested (the best footage starts at 47:00). Even though it's a pretty small token, I've really enjoyed the post-launch support Halo 4 has gotten -- between Spartan Ops, map packs, and playlist support, 343 has done a great job keeping the game relevant.
The final map pack (that's been announced so far, at least) will drop on April 8th.
Halo 4 Multiplayer [Halo Waypoint]