Patti has a week long vacation scheduled this month so I would imagine she'll for sure be on in September, excluding unplanned things like illness. Caissie announced her last vacation I want to say a month or so in advance, so I would think she would announce extended leave soon ish. I don't know how many vacations they get, but she just had a week or so I think it was in June right after the Tony's. Excluding unplanned absences, I would venture a guess you'll be good to go! Are you buying tickets to the show in advance, or are you going to wait until it's closer to be on the safe side?