The Aetherium Wars quest from 1.4 did confirm that Sampo was with the Masked Fools, which is the same faction as Sparkle. Of course that doesn't tell us a whole lot but it is something.
Haven't done the Black Swan character quest yet but here's my thoughts on the new characters:
Black Swan - Probably the biggest disappointment for me actually. She's just been kind of boring, though of course with her having a character quest I haven't started and those generally being strong there is a lot of potential for this to change
Aventurine - I actually like him a lot more than I was expecting. Unfortunately for Mihoyo not in a way that would ever make me want to play as him myself, but still. Just the right amount of unpredictability and hate-ability that he's been a pretty entertaining factor in the story. Significant contrast with Topaz who is in a similar role but the story unsuccessfully tried to get me to sympathize with her.
Acheron - Really great, but it's hard to say more when there's obviously a lot about her and her powers and motivations that we don't know yet
Sparkle - She has been pretty fun so far. I am worried they might be pushing her too far into villain territory for what I'd like, but they might not do that and it also might still work if they end up doing it. Her last scene with Sunday was great
Sunday - Expected him to be whatever and he's mostly delivered, but I did really like his last scene which might be a good sign moving forward
Robin - Well at least her song is pretty good, even if I'm constantly expecting to hear "making my way downtown..." instead of whatever she's actually singing
Firefly - I was expecting her to be the best and I was right. Her scene with Trailblazer after going through Dream's End was definitely the highlight of the patch
Misha - Not much to say but I like him so far
Sam - Design is very cool and that's all I'll say for now
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I didn't do guru this year but azuarc can be in my sig anyways.