the flood is very likely, almost guarantee to show up in halo 6. Obviously since 343 said that halo wars 2 will have a massive impact on halo 6. Artiox will be there, with his banished force. Professor Anders will also be there. I am certain we will be on a halo ring in halo 6. But we might even go back to the Ark too, seeing as how if Cortana wants the rings, why would she not want the birthplace of them? It's going to be an all-out war on the ark, and most of the halo rings will outbreak with the flood infestation. Cortana is either infected with the logic plague from the events from halo 2 and halo 3, and she wants the rings to let the flood loose, and so that nobody can try to activate them. If this is the case, it will be hard for the UNSC to do much of anything considering the power of the flood and the guardians and the prometheans all. Maybe the covenant can even reunite considering Cortana is in control of the Guardians (forerunner creations) and the Prophets worship the forerunners. This might cause the covenant splinter factions to reunite under the name of both the prophets, and cortana. It does say in the description of the halo 5 Prophet's bane energy sword that the arbiter awaits the San Shyuum's inevitable return with the blade in hand. Though, this is my only evidence that could back me up. Either way, Atriox is likely to grow in power even more and rise up and be the new covenant if my theory is wrong. If Cortana is not infected with the logic plague, the only way she could possibly be stopped is either destroying the domain, or a flood outbreak. Again, these are all just theories, and some of them make perfect sense. Unexpected things will happen surely, and some things we thought will turn out true.