Well first off I had the new gameinformer for quite some time, but was uninformed

But anyways the cover was Halo 4, so I had to read it immediately.
The release date has been announced, it will come out on November 6th, in the US at least.
They don't seem to have the full article on the site, so I will post the multiplayer article and try and sum up the other one.
http://www.gameinformer.com/b/features/archive/2012/04/16/the-changes-to-halo-39-s-competitive-multiplayer.aspx stuff. Essentially you are allowed to make loadouts, consisting of primary weapon, secondary weapon, grenade type, something I forget..., and an armor customization. The idea seems alright as long as they leave many of the powerful weapons left around the maps to find. Then they said that the multiplayer will actually be tied into the single player story so you just aren't "killing dudes". Armor also has usefulness in this one, and they said like Call of Duty, so I'm guessing a piece of armor would give you a below radar or blast shield ability, or something like that. Finally there is a mode called Spartan Ops which also ties in with the story, you and 3 other friends get missions that are updated weekly, and some kind of info to go with that. I thought that was the coolest thing about the multiplayer. Also no elites to play as
The single player seems to try and focus on John more as a person than a soldier, some I would expect some kind of backstory for him. They said that you start in Forward Unto Dawn, when Cortana awakes you, and you have to get off the ship. By the way the year is 2557, 4 years after Halo 3. So they first enemies you see are elites and grunts. Chief thought they had a truce, but they don't know. Cortana mentions that they are not equipped with normal combat gear, but there is still a fleet of them surrounding the ship. The book glasslands hinted at the fact that the truce was shaky, so it seems logical it broke up.
Then they sort of described the new unknown enemy. They tried to make it really different from the covenant, so you aren't just facing the same enemy in a different skin. They are also supposed to work together, so that facing one would be its own challenge, facing two would be a different challenge, and facing three would yet again be different. They are also supposed to have abilities or something.
Also they mention Cortana's rampancy and they say that it will be incorporated into the story somehow, she killing herself and all.
Pretty sure there was more, but that is all I remember.