343's representatives once mentioned (a long time ago, actually, just after 4 came out) that they are drawing inspiration for 5 from The Search for Spock. I assume Chief will search for a way to bring Cortana back - also evidenced by the AI chip in his hand in last year's teaser.
4 also made a strong point of how Chief was essentially a machine - a brainwashed tool used by the military. In 4, we see him "waking up" - from standing up against Del Rio, when he wanted to decommision rampant Cortana and going on his own, against orders to pursue Didact, to contemplating his humanity in final scenes. 5 will probably continue this theme - we see Chief walking alone in the desert, in rugged armor and a cloak. A classic pilgrimage imagery.
Another interesting thing I saw yesterday was the contrast between the ONI operative and Chief. One in a modern, state-of-the-art armor, the other in damaged six+ year old "piece of junk". One was handpicked from millions of children and trained to be one of the best soldiers and protectors humanity ever had, the other is probably one of Spartan IV's - a mass-production phase of the Spartan program, a tool used by UNSC to secure its domination in the galaxy. They are both Guardians of humanity, but both flawed. Chief was an indoctrinacted child soldier, the ONI operative works for a shady agency that gives GTA's FIB and IAA a run for their money. Old/New. Original/Replacement.
But what I personally find most interesting is the possibility that the desert planet might be Sanghelios. I'm really grasping at straws here, but Sanghelios was heavily featured in two pre-4 novels. Sanghelios is also rich on Forerunner relics. And, every time we saw the desert planet so far, it was barren, but we also saw some functional buildings in the concept art. In one of pre-4 books, ONI looking for a way to wipe out Elites (and literally wipe out the entire race, not just destroy their military). One of proposed methods is poisoning their crop and starving them out. What if they actually carried out this plan and Sanghelios is essentially a post-apocaliptic wasteland now?
Now this is a remake/re-release I can get behind.