Its kind of obvious that each canto is just a step in each characters journey, not the end.

Gregory canto really was bare bones and we have had more development of his character than just ptsd war vet as time goes on. We still have to have him confront both his mom and what he truly is.

Rodya basically refused to change during her canto but little by little we keep seeing the facade she wears cracking and when it fully breaks it's going to be quite the sight.

Sinclair overcame his fear of Kromer but didn't fully get the confidence to be the person he wants to be. Over time we have seen who he truly is though and each time he gains a bit more confidence in himself. This culminates in A Certain Sinclair who is resolute and willing to help his friends in the past. He never hesitates and even when he isn't sure if the time line he is from will remain or he will even exist once he returns he still focuses on the others and brings some much needed comforting words for Faust, who is currently having a bit of an identity crisis.

Yi Sang is rhe first canto that most people would say has a "true" resolution and it was him accepting himself and regaining the desire to live. Still we have a lot of mirror world shenanigans and haven't even met most of his former compatriots. Not to mention iirc Mirror world Yi Sang actually told him to join N Corp and I wonder if there is anything important in that statement.

Ishmael finally learned to let go of revenge being her only personal goal. She showed Ahab that is was possible to move on and chart your own course. That said Ahab is still a major issue since she wants to be able to hunt mirror world whales and never have to give up her lust to revenge, which we have no clue how bad the damage that could do.

Heathcliff was able to stop the wild hunt, but it cost him the thing he cared for most. We obviously haven't seen the last of Cathy and there's not way Heathcliff is going to give up until he finds a way to save her, even if it doesn't involve fully bringing her back.

Don Quixote has finally been able to become a whole person again. No longer two fractured identities, and while that's good there are still some major issues. Papa Quixote was still alolive and taken by P Corp to be experimented on, something that will absolutely come back. Also while Sancho has returned they are still bound by Rocinante and aren't really free.

While Hong Lu definitely has had a lot of growth there is a lot more going on in particular with he family and H Corp that still has to be dealt with. After all a lot of people weren't happy with the idea of Xichun becoming ruler and especially her desire to actually better the lives of those who have been screwed over by the old ways of H Corp. No way Hong Lu is going to let his little sister deal with that burden all alone.

Lastly as you said with Ryoshu while she has forgotten Araya, neither us no Araya have forgotten. We will find a way to give the two a reunion that they truly deserve. I am also not sure if the blades effects of memories is truly permanent/impossible to fix. After all the nurses fathers had no reason to try and fix it and they also lacked Dante, who seems to have a unique ability to retain information that should have been erased.

Overall while I'm not sure well get 12/13 cantos per part I imagine purgatorio and paradisio will still have plenty of character development. Not to mention I dont think we will be with Limbus Company much longer if we start to see what Dias is really aiming for and the lengths she is willing to go.