So I've been thinking, is it possible for the next map to be located in Germany? It seems like "The Greater Force" has the ability to teleport the group anywhere around the world. The easter egg will most likely be something to do with charging a tower. After going reading over the entire storyline, I've come to the theory that Richtofen and Maxxis are having the group activate towers at all the previous bases that Richtofen used to experiment with Group 935.
Is it possible that the final map could be the Moon once again? Maybe after all the towers are charged, "The Greater Force" will bring the group to the moon to meet Richtofen?
These are just some theories I haven't really developed into too much detail.