User blog comment:Argorrath/Treyarch posts a message of zombies; possibly hinting to a DLC 4/@comment-14746056-20130807062849

Scince a good amount of the letters point towrds france, I'm guessing the Effile Tower will be the Last conponent in either of the germens Plans. The gun is possibly just a new wepon for the players or hinting that WaW Gun will be avalible. And the Periodic Table so far is the only one confirmed to be made by anyone specific (Maxis)