Halo 4 is going to obviously take place after halo 3. it will take place probably on a forerunner installation besides a halo または a forerunner planet. who the enemy is is unclear but i expect forerunners to be directly involved and flood.
Since the Covenant were defeated and the Flood were perhaps annihilated, I'm guessing Master Chief will just be dealing with もっと見る Forerunner Sentinels and maybe a new threat. What Halo 4 will hold is still unclear.
Halo 4 is going to take up where the Halo 3 legendary ending left off. In the teaser trailer it shows the Chief facing off against a forerunner shield world, または something like that, but it will definitely be mostly about the forerunners.
Halo 4 is about the return of the Master Chief. As seen in the Legendary ending for Halo 3, the derelict ship Chief is stranded on approaches as Forerunner shield world. Chief will face Covenant, Forerunner defense systems, the Didact (who is a very prominent Forerunner along with the Librarian) and possibly deal with the Precursors. The UNSC Infinity which is the newest (and largest) UNSC ship ever built crashes on the aforementioned shield world with Chief on it, carrying a buttload of new Spartan IV soldiers. Can't wait!