Eurogamer just posted this article, claiming that their sources have told them that the new COD is indeed called COD: WWII and as the name suggests, takes place during second World War
http://www.eurogamer.net/articles/2017-03-27-this-years-call-of-duty-is-set-in-ww2
"Developed by Sledgehammer Games, the studio behind 2014's COD: Advanced Warfare, this new COD will be the first to venture back to the series' World War roots since 2008's World at War.
Images published on YouTube channel The Family Video Gamers last weekend showed logos and box art for "Call of Duty: WW2". Eurogamer has since verified this does indeed relate to this year's game."
http://www.eurogamer.net/articles/2017-03-27-this-years-call-of-duty-is-set-in-ww2
"Developed by Sledgehammer Games, the studio behind 2014's COD: Advanced Warfare, this new COD will be the first to venture back to the series' World War roots since 2008's World at War.
Images published on YouTube channel The Family Video Gamers last weekend showed logos and box art for "Call of Duty: WW2". Eurogamer has since verified this does indeed relate to this year's game."