NOTE: THIS IS NO SPOILER, JUST A THEORY MADE BY MYSELF OF WHAT THE RECLAIMER TRILOGY COULD BE ABOUT! I AM AWARE IT IS A LITTLE CRAZY!
A halo has always been present in the original Halo Trilogy even if it was just a glimpse of it; therefore Halo 4 will not be different. In the video showed in E3 we could see Halo 4 demo’s main menu a Halo ring as well as Requiem shattered in some ways, probably hinting that during the campaign OR spartan ops we might see a Halo array as well as the destruction or semi-destruction of the shield world. The destruction of the world might be similar to the destruction of the Shield World of Halo Wars leaving most, if not all, of the world destroyed.
During Halo 4 we might meet with the destruction of Requiem, an event that could be caused by the humans as well as the ancient enemy (most likely The Didact). Human’s reasons for destroying it could be to avoid the ancient enemy from leaving to go to Earth or somewhere else that might lead to the human race’s extintion (a place like the Ark for instance) and/or attempting to destroy most if not all of the enemy’s army or the enemy itself. On the other hand, the ancient enemy’s reasons to destroy the shield world might be to destroy The UNSC Infinity or trap it with the blast of the world’s destruction so they can not go back to Earth and warn the humans about the existence of this ancient enemy and their purposes. In the E3 2012 Gameplay Demo Trailer, Cortana screams: “I will not allow you to leave this planet!” meaning that she has gone rampant and will try to avoid Chief/humans from escaping the Ancient Enemy’s “web”. Either way, if Requiem is destroyed, the menu would have hinted a crucial part about the game leading to other theories like the interaction of humans with a new Halo Array.
If the Reclaimer Trilogy follows the path of the original trilogy, it might contain one or more Halo Array in each game. If the game takes place in an array, it would mean that the galaxy is once more walking through a thin line and its life could be sent to oblibion once more. There are a couple of reasons why a Halo array might be fired but the most relevant seems to be the flood. The player, already knows that the flood was wiped away with the destruction of the Ark but a spore could have escaped the explosion or the parasite could be residing in somewhere else of the galaxy just like 343 Guilty Spark claimed in one of the terminals of Halo: Combat Evolved Anniversary. If so, it might spread during the trilogy and invade Earth destroying most of it and/or attack the ancient enemy. Given the situation, the ancient enemy might want to activate the Halo arrays probably using a reconstructed Ark (remember that in just a lapse of days / weeks / months the array destroyed in Halo: CE was almost completely rebuilt for Halo 3 meaning that with given rate, the Ark could be rebuilt by Forerunner AI’s at the same pace) to clean the galaxy of the Flood as well as humans while staying in a shield world just like in the past. On the other hand, humans realizing that they have lost the battle might as well follow the steps of the forerunners and clean the galaxy from the flood, however, destroying all spores this time to avoid future expansion of it. The remaining humans could escape to a shield world or could follow the forerunner’s protocols to assure the existence of life in the galaxy by “planting” different species post-firing throughout the galaxy just like it was showed at the beginning of Halo: Legends.
The plot presented in the post above, would contain a series of twists that would keep the player’s attention in the game while having that element of surprise that make the Halo series one of the best (if not the best) in the gaming industry. The ending for Halo 6 could be something like this (with a soundtrack similar to this), which would be really inspiring and keep that spark of sadness, completeness and heroism present in the Halo Series for it had to be done; it was their duty.
Thoughts?
P.S. Forgive my english for spanish it just my second language.