Multiple Valkyria Chronicles 4 product listings have gone live in North America, and they all have the same thing in common. Each one says the game will be released in the region on October 16, 2018. There are U.S. listings for the PlayStation 4 and Xbox One versions, while the Canadian listing is for the Nintendo Switch. Sega has not confirmed anything yet, but says it will be in the Americas and Europe in Fall 2018. (Thanks, Wario64!)
Sega has also updated the Valkyria Chronicles 4 website. The World, Character and System sections have all received some new information.
Valkyria Chronicles 4 will come to the PlayStation 4 in Japan on March 21, 2018, followed by a Nintendo Switch release in Summer 2018.