...aside from that soft reset from the movie? To be honest, Ninjago seems like a tired series, there's not much they can do that's new and won't be torn apart or compared to another year.
The core characters are the same, the villains fall into categories. Bionicle did things fresh each year whether it be changing the style drastically (Compare the Inika to the Mahri or the Hordika and the Metru) or changing the theme (Inika to Mahri) or even just changing the villain (Bohrok to Rahkshi).
On the Castle theme
Also because I'm super late to the party on this one, I checked Eurobricks and cannot find any support for the castle theme. I think the reason castle has run as long as it has is for 2 reasons.
1) It is not a continuous story theme, it has breaks wherein things are changed in the next iteration, knights kingdom is different from kingdom, some have magic, others don't and characters change.
2) It's generic as heck. It's literally just castles, people don't need to get invested into it to love a castle, I don't need a backstory for a cool castle.
There is a fanbase on Eurobricks for castles sure but that doesn't mean they're fans of the castle theme. Bionicle had a rich story to it, that's why the fans have kept it going for such a long time, castle never did, I never wanted to learn more about castle and I did buy a lot of castle sets.
Ending with a new thing to start a fresh conversation which someone will ignore due to the content above, I don't like lego city being so flat, chuck in a bridge or incline somewhere, even if its a small bridge over a pond.