I'm catching up on this thread, and I feel like I'm missing something when it comes to this Mii costume guy - what makes him a valid source of information? He got the Cuphead costume right, sure, but that was a high profile release at the start of the year, and we had just gotten Sans a few months before this message.
Maybe someone who's better versed in this whole thing can fill me in, or maybe it's better to take it to private messages to avoid derailing the thread, but I'm not sure how 1/9 of those costumes being in the game makes this person an accurate source of information. I'd understand the trust if he had guessed Vault Boy, Ninjara, or a Rabbid in addition to Cuphead, but an 11% success rate doesn't exactly fill me with confidence.
I could say that we're going to get Mii costumes/hats of the Knight from Hollow Knight, Mallow, the Cacodemon from Doom, Emil from Nier/Nier Automata (who, given his design allowing for a full mask like Cuphead or Sans, could come with one of the songs from that game like
this,
this, or
this), Cynthia from Pokemon, Buck from Halo 3 ODST, Adeleine from Kirby, Dr. Cortex from Crash Bandicoot, and Knack, but if one of those happens to be right by sheer coincidence, it doesn't mean that I actually know anything about what's coming up.