Origins is depicted as a prequel. However, I don't see it as a prequel. While the trailer strongly suggest that this is the beginning of the saga, we've been moving forward the entire time. The current gen weapons are in the map. While this may be debunked for gameplay reasons it could be proof that this map is not really in the past. What a tough thing to explain is the young appearance of our characters, what does not make sense is that they meet here. The radios from Call of the Dead suggests that Richtofen meets all our characters in 1945. It also states that Dempsey was captured and Richtofen names him The American. Which is weird considering that they met along time ago. The eyes of the zombies is also interesting. Before the gameplay was shown the theorized eyes were red, just like MotD. But they are not, they are orange (Maxis anyone?). Considering that Maxis his ultimate goal is to be reunited with his daughter did he reformed the past? But that makes me think that the ending for buried must be Maxis.
But why get two endings to chose from then?
So if we look at Origins and the relation between Maxis and our characters, his goal is to kill the characters then. To stop the future from happening. As Treyarch said that the ending for this will be more 'awesome' than the moon ending wouldn't it make more sense if it would go this kind of direction than just a prequel? Zombies will return, so what kind of cliffhanger can be expected from a ordinary prequel if we already know what happens after Origins. Basically this is my perspective why I don't think Origins is a real prequel.