I went for December. Although it could easily be as early as October, they're not going to be majorly hesitant. But it's hard to know how many rounds of auditions there will be. I imagine they'll tell us as soon as they can, but I couldn't say how arduous the process would be. Schedules and contracts and multiple rounds of interviews and auditions, I could see it possibly taking until December.
That said, I haven't done much music-based speculation, lately. I'm usually looking at TV shows, which take ages to confirm anything as it's such a complex and multifaceted animal with pre-production and confidentiality and all that dancing, so I could easily be adding weeks onto my estimate for no good reason. And probably am.