Well, from the way things are looking, and the fact that they confirmed she would be released after the Worlds patch (7.18) and before the preseason patch (7.22), that leaves a timeframe of 7.19 - 7.21. We know she won't be released in 7.19 since the 7.19 PBE cycle has been up for days now with no sign of her. So most likely, she will either be released in 7.20 or in 7.21. I'd personally bet 7.20, since they probably don't want to cut it so close to preseason. Again, just my reasoning, don't take it as gospel. If she IS being released in 7.20, we should see her champion reveal come up a patch in advance, meaning that we could be seeing it as soon as next week.