at the end of halo 3, the chief is approaching an unknown planet. my guess was this was a forerunner shield world. bungie invented the forerunners but never elaborated on their origins or what happened to them. we know they were an advanced race, and we know they were in a war with the flood, and we know that they ultamately wiped themselves and the flood oout with the halos. other than that, we know nothing about them so it was a logical assumption that the chief and cortana would crash land on a forerunner and unlock the unknown past. odds are we will be introduced to a new monitor, and will probably spend most of our time fighting flood. now, the other assumption is that the chif and cortana would leave this new world in a forerunner dreadnought and with cortana piloting, take all of the new information back to earth and give it to the UNSC. now this would be an interesting ending because the UNSC thinks all of the legendary Spartan II's are dead and having the chief show up with cortana in a forerunner dreadnaught loaded with data on the forerunners would be a massive and pleasant surprise. now as for the chief, he could be reassigned to train an army of spartans in the event of another war. much like kurt 051 was the one who trained all of the Spartan III's. that would be an excellent end to the story line which bungie left open. the chief would be alive, and the commander responsible for training a new army of spartans. and another interesting and pleasant twist would be that cortana managed to use forerunner technology to be able to prevent her own rampancy and be able to give this information to ONI which would be able to use it on all new AI's and these new AI's would be able to live forever instead of only 7 years. what do you think of that?