How should Samurai Warriors evolve?
If Samurai Warriors were to ever get another entry, I think it would need to have a step forward in its game design and mechanics. Especially after DW:O, I don't think a new Samurai Warriors can afford to just be "the previous game but more refined", which I felt was largely the problem with Samurai Warriors 5. I think a lot of the complaints regarding SW5 reboot nature and the changes that came with it would have gone down a lot better if the gameplay had some major step forward and innovation, but for the most part, SW5 was just a more refined SW4, which thus didn't justify it being a complete reboot and overhaul.
Personally, I think Samurai Warriors really needs to take a look at how its more objective based focus on musou stage design is supposed to work. It's sort of the thing that separates how SW battles flow compared to DW battles, but I don't think the series has really iterated on it that well. If DW battles at its worst can be described as a linear set of objectives, then the latter SW games are absolute explicit about it, where every stage can be boiled down to a literal checklist of events and objectives. I think a more freeform and open ended approach to completing and progressing through objectives would be interesting, like perhaps an objective could have multiple ways it could be completed and depending on which method was chosen, that also affects how the next objective plays out.