6.6 might just be the start
I've been seeing almost everyone being (understandably) really upset but after 6.6, I actually have more hope.
They spent so much effort on everything related to him, from lore to design, animations, voice etc.
If they really just wanted to kill him off permanently, they could've done so much earlier and just ignored any backstory writing. But no, instead they introduce even more.
There are already many unresolved questions and now they add things like losing his compassion at age 8 specifically.
Not only that, there's also his idea for revival with Pantalone.
And after so long, we still have no clear picture on his motive. Why was he chased away the first time? Why exactly do he and Pantalone dislike fate so much? Just because they don't like feeling controlled? Or is it something deeper?
Wanderer mentions wanting to investigate Dottore's motives in the end talk with Nahida. Which means there will be more.
I understand that Dottore had to be "cleansed" by fire as his crimes were shown much more upfront and some had more universal impact on Teyvat than other morally questionable playable characters.
They constantly talked about time being able to erase hatred and Dottore mentioned people tend to stick to first impressions, a bit like foreshadowing.
They also mentioned the importance of the number 3 compared to 2, meanwhile his soul was only split into two parts.
They also specifically mentioned he was human and this entire quest was connected to Nicole who is an angel and talks about wanting to help every human. In her trailer they even hint at understanding a demon king's motives. Even if Dottore wasn't meant by this, it would still fit him.
There was also the highlighted importance of bad events compared to good ones. And, of course, the entire fate system being gone now.
Dottore also seems to have wanted the quest's events to happen and Pantalone talks about having planned every single step to a detail.
I think they're playing the long game with him, I mean they have already this entire time.
Still, all in all, I'd say despite points of hope, it's better to be prepared and have alternative things/ sources of entertainment to focus on. I'll wait for Snezhnaya and see what happens then. The idea of reviving someone by transfering memories is nothing new in Hoyoverse and would fit the preservation/ remembrance aspect of Snezhnaya. And in Collei's dream, even though the characters switched their roles, they were still themselves fundamentally (HYV has also mentioned characters staying themselves at other times). Also, they have a tendency to explain every (important) villain's motives or even redeem them (even if people don't like it). They even ended up portraying the Honkai itself in a good light.
Just my opinion, Idk if it all makes sense but hope is there for me.
And there are many more points I could probably mention.