Koei Tecmo and Omega Force have announced Warriors Orochi 4, the first brand new numbered entry in the series since Warriors Orochi 3 in 2011. It will launch in Japan in 2018. Platform(s) were not announced.

Like the Dynasty Warriors series, the numbering of the Warriors Orochi series is one digit higher in the west than it is in Japan. This is because the second Warriors Orochi game, which is titled Musou Orochi: Rebrith of the Demon Lord in Japan, was released as Warriors Orochi 2 in the west. The actual Musou Orochi 2 was released as Warriors Orochi 3 in the west. The new entry
announced today is titled Musou Orochi 3 in Japan.

http://gtm.you1.cn/sharedfiles/filedetails/?id=1335994339

hope they add character from DW 9 but gave them unique move set

source: https://gematsu.com/2018/03/warriors-orochi-4-announced#OZgWWGU6EHfiQ5qk.99