Well, I remember a similar discussion in the past which point out each girl circumstance in regards of Handshake interaction. Won't point out the other 3 (as it's obvious by reading the ppl report). But for Yone (which you specifically ask), I recalled there isn't much new reveal about her personality in Keyakake, her mobame, or any other media. Remember her love for microorganism? Her refusal to use shared stuff? That's when she sell decent. Because fans has topic to talk about with her. But you can't keep fans devoid of new topic/information for too long else they will lose interest and gone, isn't it? As for situation change, errr.... that will depends entirely on the majority of fans hype. We all can wish for these 4 to rise into kami-tier of Keya big sellers. But if the bigger circle than us desired more other, fresher members instead, few we can do.