It is due out in FALL 2020, apparently. (The title icon on their website also says 'coming Fall 2020'.) Looking forward to hearing a bit more. All we have to go on right now is that they say it will be a new engine with new graphics, and the title logo, plus a short description of the plot. The game will be distributed in Europe by Nintendo, and the game is said to be developed by Natsume and Rising Star Games. Graphics are said to have been 'updated for 2020'.
Title graphic:
EDIT:Natsume wrote:Can you imagine a world without tomatoes, strawberries, or even cabbage? In the latest entry in the Harvest Moon series, that’s the situation players will find themselves in. Only an old book gives hints of what once was… Buoyed by a mysterious discovery, players will find themselves setting out on an adventure that spans not only their hometown but the whole world! What kind of people and places await? From the gorgeous beaches of Halo Halo to the snowy mountains of Salmiakki, there’s literally an entire world to explore.
Harvest Moon: One World will also be on PS4, and it has a cover image: