Yes , I think 5th dawnbringers book is very likely and there is enough room if we say :
November 2023: Dawnbringers book 3
December 2023 : Xmas boxes (Belakor legions,Seraphon,Soulblight, Ossiarch)
Januray 2024 : FEC armyset
February 2024 : Dawnbringers book 4
March 2024 : FEC Full release
April 2024: Dawnbringers book 5
June/July 2024 : 4th edition launch box
I am sure at the Warhammer day October 14th they will show updated roadmap