AMAZING TRAILER.
Also yes that is Dr. Catherine Halsey undoubtedly at the end. Noble Six is not Master Chief since thats physically impossible for multiple reasons. Halsey is simply comparing the too of them since they are similar. Here's why.
1st. Master Chief in orbit during the events of Reach trying to protect / destroy vital com data information from the Covenant, he himself wasn't actually on the planet and ends up fleeing on the Pillar of Autumn before Reach is even glassed. He actually arrives at the first Halo soon after Reach falls and is in slipspace during its destruction.
2nd. Noble 6 is a Spartan III that was created by Kurt and his group on the planet Onyx and was completely separate from the other main group of Spartan 2's. Their existence was known by almost no one whereas at this point in the war Spartan 2's were well known by both the civilians and military. Chief is a Spartan 2.
Now for the biggest question from the trailer, who on Earth was Halsey talking to and what is noble teams final legendary mission they are embarking on? A couple theories on this are that Halsey is either talking to Aunti Dot an AI that has been revealed through looking closely at footage from Reach who we are unsure is a "smart" AI, or she could be talking to Cortana's sistrer who was supposedly de-comishioned and destroyed once Cortana was created but Halsey may have saved her since she has a long history of breaking the rules. Also there are other people who are in the room who she may be talking to, this picture proves it.
