seeing as how time travel is a main theme in zombies, it really could be anyone in the zombies storyline who is a female. Even if sophia was dead it isnt insane to think the team could have time traveled to a time where she wasnt dead. the zombies story isnt really time definitive, so its hard to ever call a part of the story the past, present, or future, (unless i totally missed something) because nothing happens in the past or future, it happens when the characters were there! when people say it could be samantha in the poster, people start talking about dates and and ages to see if it adds up, but whos to say it has to do with a future time? it can even be a new character, just as BO1 brought in new characters so could BO2. Until we play the game or are told who the woman in the poster is, I think most speculation will lead to IT CAN BE ANYONE! New or established character. From anytime. Only time will tell.
Im excited to find out though