Slow down, guys. These "Letters from the Field" extend the canon in anticipation for DLC4, but why do you all expect that they describe the next map? Treat these letters independently until we have complete confirmation.
Now, let's get back on-topic. This is an alternate universe. These are the known differences: the O4 are going to meet during WWI instead of WWII, and 935's operations in Breslau and Griffin Station are now being performed before its conception and in German-occupied Northern France. We know that there is testing with 115 by an unknown organization (935, Illuminati, Germany, etc), that organization has made technology with or without 115 that appears like lights in the sky and metal men, Richtofen is leading the 115 excavation, and Maxis has obtained a pistol two years prior to the other letters.
Speculation: The first letter is Richtofen writing in third-person (like he sometimes speaks). Element 115 is affecting Maxis's sanity, and the man now plans to assassinate Richtofen with his Mauser from a distance (attachment scope). If any of this is related to the story, the last map might be the outcome of this switcharoo alternate universe.