(but I have no idea when the retirment announcments will come so... eh?)

Usually top retirement annoucnements are roughly six months-ish from actual retirements, sometimes a little less for musumeyaku.

As for how Kimu would fit into tsukigumi, I feel like tsukigumi has been in a state of flux for a while now. Given that they don't have a firm identity at the moment, it might be an okay time for someone (Kimu or otherwise) to slip in there?