Since Kaede is already somewhat good I'm hopeful for her.
Come to think of it, they did announce the new single rather quickly - compared to last year. Especially since Kobushi is overdue for a new single, their last was released half a year ago (granted, they had an album in between).
Maybe it's because they want the miso soup song out for the commercial campaign. That might be the reason why they couldn't wait for Masaki, especially with the chance that she might not be able to come back in February either.
I'm not too much into Masaki's way of singing or performing, so I'm probably not going to miss her, but some people over there at H!O are the icing on the cake, once again. Sure, UF wants to release as many songs as possible with Masaki out. And sure, Masaki not being included is going to hurt their sales so much. Without Masaki, Sashihara won't be interested in MM anymore.
Honestly, some of her fans make it really hard to get interested in her. (I know that's petty, but they're really off-putting.)