Warriors Orochi 4/ Musou Orochi 3 will be a soft reboot in which the DW and SW characters got their memories erased by the mystics sending them to their respective timelines however a new threat in which both worlds merged thanks by Zeus and the Greek Gods.

It was announced that Non-Historic Guest Characters (Ninja Gaiden/Dead Or Alive characters along with Sterk from Atelier, etc.) won't be returning to the game while historic characters guests like Joan of Arc from Bladestorm and Achilles from Warriors: Legends of Troy (who might play role in the game) might make it
https://www.hardcoregamer.com/2018/0...threat/298829/