After doing some research I have put a couple things together to come up with a theory on what the next map will be and why they are going there.....

First I will begin at Shi No Numa: Over the radio you a man talking about the "experiment"(which is the zombie experiment with element 115) and he says you need to find Dr. Richtofen or Dr. Max( [ Register or Signin to view external links. ] listen at 1:38) to help you figure out what's going on. Only Dr. Richtofen shows up and Dr. Max is no where to be found. Plus there is meteor there which the main source of element 115.

On to Ascension: Many of you remember the huge easter egg with the "5th guy"(my friend came up with the idea of a 5th guy) where everyone can get death machines for a couple minutes right? Watch this video "http://www.youtube.com/watch?v=zl2vtYpNVaU" to refresh your memory.(yes i was in this video and was the first one to upload the easter egg to youtube with help from my friend Robert) During the whole easter egg you are getting power and supplies to some random guy trapped in a teleporter or black hole possibly to send him to Shi No Numa, which was his original destination. This is Dr. Max.

Call of the Dead: I'm sure everyone knows about the current easter egg achievement to send the original 4 to "paradise" as the achievement calls it. I believe they are stuck in a similar machine that Dr. Max is and Dr. Richtofen is trying to meet up with him. Using this information plus the torn poster corner from the loading screen of call of the dead(looks like jungle tree leaves) I can only assume that the next map will be some sort of jungle.

Add it all up: In the next map they are going somewhere similar to Shi No Numa and going to meet up with Dr. Max for the source of element 115. Maybe they will use the teleporters from to make it to freedom.

Let me know what you think and if you have anything good to add let me know! Thanks