Wait, "judging from the screenshots"? Even if the characters were voiced, how would you come to that deduction from the screenshots alone?
I was joking about that sentence. How the characters' voices sound like, canonically, are (afaik) left open to interpretation, which seems good for fanworks (versatility, etc.), but that's just my bias, or opinion, or whatever it's called here.
I was thinking of something today. Tasofro might (as an option, mind you) focus on presenting characters that haven't appeared in previous fighting games to introduce new playstyles, and then (with more time) put an expansion/patch with the "veteran" characters, because if they invert this process (let's say, having most of the previous characters), it could be more difficult to make the game feel fresh (people could focus their attention on the differences/similarities between the moves/playstyle from this new game and the other ones and some could feel that they're playing "more of the same thing").
tl;dr: the opportunity is there, for the coming of lots of "new" characters in a touhou fighting game (with the revamp of sprites/backgrounds/code/system/etc.)