Halo 5: Guardians released in October 2015 to a decent reception from fans and critics alike, holding a respectable 84% on Metacritic. That being said, the game didn't sell quite as well as past entries -- and it seems that the adoration and reverence for this series is waning fast. Regardless, it seems all but certain that Microsoft's E3 2017 will close with a trailer for the next installment in the franchise, despite the studio saying it won't make an appearance.
It was reported a while back that Halo 6 will feature Master Chief as the sole protagonist, with no other playable characters. This comes as a surefire song to the ears of Halo fans everywhere, as the series has often gotten bogged down with secondary characters like Locke. For a while, it even seemed like developer 343i wanted to replace Chief with Locke going forward. Thankfully, it sounds like that idea has been scrapped.
Halo 6 will definitely make the Xbox's upcoming slate sound a lot better, not to mention it could be a showcase for the graphical power of the Scorpio. 343 Industries has said that Halo 6 will not appear at E3, but developers often lie about these kinds of things, and it's hard to imagine Microsoft not pushing for a CG trailer at the very least.