Going by RAH, they announced the release date on October 26th and the DVD was released on November 29th (US / 27th (UK). So if they want to do the same thing again, they still have around a month to make an announcement. The end of November seems like a great time, since even her US tour would be done by then. So she'd have time to do some promo too

(who am I kidding, we all know how this is going to end up...)