Is it the planet that is shown near the end of the Legendary Campaign cutscene? If it is, it is probably Marathon.
i definitly know its not onyx or earth. im not even sure if rainbow planet is real, lol. im pretty sure theres no such thing as the ark center planet. so ima have to go with forrunner shield world or marathon. the fact that u brought up marathon makes me think that halo may be integrating in with marathon somehow (not counting security helmet or red vs blue).
It is obviously machine so it is either Forerunner or Precursor but the latter is more likely. Onyx was effectively disassembled into the sentinels and the planet didn't look like a bunch of sentinels. Onyx was a shield world but it was covered in vegetation so it is unlikely that is a shield world because the Halos are all similar so logic dictates shield worlds will be similar. It is obviously not Earth. Marathon is a highly unlikely possibility but still a possibility. The Ark Center World would probably be near Ark if it exists but no info suggests this place exists. Unfortunately I can't remember if the Rainbow World is supposedly Forerunner if it is, it too would probably covered in vegetation. So the possibilitys are Marathon, a Precursor world, or the Rainbow world if it is Precursor and not Forerunner.
As you well know, the fight might be over, but that doesn't mean the ride is too. I would say that it is the secret home of the forerunners. You know, they just get there by accident like in the beginning with Halo.
well if its a forerunner planet theyr not going to make another game beacuse they would pose no threat, and there are no other enimies so there would be no halo 4 beacuse there will be no fights to feul the game.