So I will start by saying I really hope the open world Halo is more like what they did with Gears where you still have great story telling but add more side stuff to dip your toes in. By that I encompass all good things like side quest stories to tell us about the world or more about the main quest, maybe some dialogue options that can create minor or major consequences on Zeta Halo, and of course lots of cool customizations to seek out and find.
Onto my theory.
So what if in light of trying to go open world they just go full on assassins creed with it maybe not in infinite but the next game after. By saying this and with the possible deletion of Cortana and a new AI entering the fray. They could retire Chief at the end of Infinite and make him the new Captain Keyes or some -Yoink- and then the follow up game you create your own character lets compare it to a Bioware game and you get this new AI from infinite and boom 343 has a new blank canvas. I don’t know those are my short thoughts on Chief and Cortana splitting because I just can’t see Chief without Cortana. 4 was a great story but felt different without her then they ended 4 perfectly for Cortana and I was good with it then 5 was like F that lets make her the baddie and have no clue where this story is going lol. So hopefully Infinite will reunite Chief and Cortana and give them both a fitting end together ensuing the walk off into the distance giving way to the new. Thoughts?