Don't get me wrong, I love this game. But I think a few new things should be added to it.
1. New vehicles. A UNSC flying vehicle in multiplayer would be great, like a Falcon. Also, a Revenant for the Covenant would be a good addition also because they have no "Medium-Sized" vehicles in this game, it goes from a Ghost to a Wraith.
2. Some new larger maps. The maps in Halo 4 are great, they have great scenery and are great in multiplayer, but I think a larger map that would be great for forging would be awesome. I'm thinking another Forge World?
3. More Multiplayer game types. I know SWAT has recently been added, so I can tell that game types are already being updated. Action Sack was always very fun, with Hockey, Dino-Blasters, Splockets, Shotty-Snipers, etc. Also, Invasion was always great and very popular because it combined Slayer, BTB, and Objective all in one.
4. Elites in Multiplayer. This one kind of goes with the Invasion thing. Elites were always fun to have in multiplayer, especially in Halo Reach. They had fun game types such as Dino-Blasters, Elite Slayer, and of course, Invasion. They just made it more fun.
These are some things I think should be added to Halo 4.