I have reason to believe that our original Halo 5 teaser from E3 2013 (Chief in the desert with Guardian) could very well take place after the events of Halo 5: Guardians. During Halo 5: Guardians, Chief sustains the blunt damage to his visor from Locke, Guardians rise, and his relationship with Cortana suddenly takes a profound change. Symbolically, each of these appear in E3 2013’s teaser trailer. Chief’s visor has already been damaged, he was obviously looking for this Guardian’s location, clenches Cortana’s chip in hand to symbolize what he had lost, and the cloak to suggest that maybe Cortana has purged the galaxy of all functioning electronic technology besides herself, other loyal AI, and of course, a legion of Guardians to enforce a new age order. The Hunt the Truth ‘opposites’ trailers can also hold their own in suggesting those events take place after Halo 5: Guardians. A damaged Infinity in the sky (as Cortana was so interested in its whereabouts), John’s dialog to (who could presumably be) Cortana, and so on.
With that being said, it is perfectly possible that 343 has already foreshadowed a Halo 5 part 2 before our eyes; one that was not too well delivered on, given most people’s disappointment and feelings of incompleteness with Halo 5: Guardians’ campaign. Incidentally, Halo 5: Guardians ends on the planet Sanghelios, where our original teaser trailer seemed to begin. Halo 5: Guardians’ post credits also confirm that Sanghelios will continue to be a setting in the future. This is pure speculation and drawing inferences of past and recent advertisement media for this title. Just something I’ve been thinking about, and I thought I’d share them with you! Thoughts, community?