So if you have an Arcade unit, well, sucks to be you. Of course, you can just buy a bigger Xbox 360 HD or use a USB stick for the installation process.
This bit if info was undisclosed by an Xbox product page which states the following.
At a minimum, you’ll need at least an 8GB USB Flash Drive or an Xbox 360 Hard Drive to play Multiplayer mode in Halo 4. For an optimal experience playing with an Xbox 360 Hard Drive is highly recommended. For Xbox 360 4GB, Arcade and Core consoles, the Xbox 360 Hard Drive is sold separately. See below for more details on the storage device options available for Xbox 360 and Halo 4.
So, I take it that’s to make loading faster and maybe to house the Spartan Ops co-op missions, no? Seeing as Microsoft has already said they’re going to be doling out these missions post-launch with regularity, I’d advise you to get a bigger HD now.
Halo 4 is set for release on November 6 for the Xbox 360.