I'm not sure about the newer books, But I do kinda have some ideas about what should happen next. I haven't read all the final book, but I have seen some spoilers. I apologize ahead of time if I suggest something that could not happen because some cat died.
My top ten of what should happen next.
1. I think that some of the cats should travel to Skyclan and star a neighboring clan there. (In a third Skyclan special edition book.)
2. Thunderclan should have another evil like cat, but with different motives and intentions to the other evil cats.
3. Crowfeather and Leafpool get back together.
4. Briarlight regains some use of her back legs, but it's very limited.
5. The clans protest against medicen cats not being aloud to have mates and fail in the endeavor for a while, then accomplish that task about a year after giving up on it. (Drama purposes)
6. Starclan and the dark forest becomes less involved in clan affairs.
7. Shadowclan drives Riverclan into Windclan due to a war Riverclan caused.
8. The two kittypets at the twoleg house start kittypet clan.
9. More forbidden love.
10. Better spelling. (Both me and Erin Hunter.)