Okay so here is a sum up of all the Halo 4 material that I am aware of.
Halo 4 will most likely feature the Forerunners due to what is in the concept art and from what the planet looked like in the trailer.
The planet in the trailer is most likely Onyx as a guess given from the recent ONI data leaks.
You will get most of your materials from the Forward Unto Dawn and it will serve as a base in the early part of the game.
The Spirit of Fire might make a re-appearance due to the nature of Halo Wars' ending since I can't see 343 leaving a game that ended by setting up a sequel.
There was an unidentified leak that said that there could be destructible environments. This has never been confirmed and is in no ways official.
Master Chief DOES NOT have a jet pack in the trailer. The devise is most likely what is called a thrust pack which is only useful in space and possibly water. A thrust pack also works with canon.
There will be a pistol that works similarly to a rifle grenade.
Cortana will play a huge part in the new Halo trilogy, it will most likely follow her decent into rampancy since she is almost 7 years old and Frank O'Conner has brought up the fact that she is getting old several times.
The game will probably have the UNSC due to the fact that there are Marines and Pelicans in the concept art.
Rumor:The Precursors could be a possible enemy, possibly "The Timeless One".
According to Halo canon, time travel is not impossible. Also if you include I Love Bees as canon then it is confirmed that accidents during slipspace can cause time travel.
I just did this off the top of my head. Please comment with anything I missed!