Persona 5 Strikers didn't get any DLC content at all (though I admit it wasn't really a warriors game).
Not saying that there won't be any DLC for this game, but there are some indications that may suggest Koei released Three Hopes as a complete package just like P5S.
- They put the 4 Ashen Wolves (DLC in Three Houses) as well as Rhea, Sothis and Arval (who aren't even playable at all in the story and can't even appear in camp), in the base game, but not 4 other playable characters from Three Houses base game (Gustave, Hannerman, Cyril and Alois). It doesn't make much sense from a promotional standpoint since you want to keep popular characters as DLCs, not the other way around. It would have been much better to keep the 4 guys in the base game since they all appear and played roles during the story, and keep Rhea, Sothis and Arval as DLC characters with new, unique classes as opposed to clones.
So my guess is Koei will decide whether they are making DLCs or not based on the sales number. If the sales is below expectations, they can just walk away and without having to worry about outrage from fans that popular characters like the Ashen Wolves and Rhea & Sothis are not playable even though they literally just did the bare minimum since none of these characcters have unique moveset.