Military advisors and futurists help
For the most part, Call of Duty has dealt with past or present scenarios up until now. But, Advanced Warfare is going to move the story ahead forty years. How can Sledgehammer Games craft a realistic future when it's so far away?
Long story short: it's enlisted the help of a lot of military advisors and futurists to help add authenticity. This video explains some of the specifics of their roles. It also explains how the developers are putting an emphasis on story-telling in this game, something that many would probably emphatically say was missing from several previous installments.