SEGA have just announced Valkyria Chronicles 4, set to be released in 2018 for PS4, Switch and Xbox One (The japanese PS4 version will be March 21st, 2018). It will be receiving an official worldwide release.
The Famitsu article [https://www.famitsu.com/news/201711/20146269.html] has some more screenshots and informaton, with more info coming on the 22nd of November.
Looks like they'll be focusing a lot more on the Federation (the player side) and Empire this time.
Hitoshi Sakimoto, composer of the previous games, will be returning as well as previous character designer Honjou Raita.