How confident are we that Zelda BotW 2 will be shown next week?
Not much at all.
If they are planning on releasing information anytime soon, I don't know why Nintendo would release that Aonuma delay video a few months ago. Most likely, I think we'll see it in September or even February if the game gets delayed to later 2023.
The one thing is that if Nintendo wants to announce WWHD this direct, there will be a lot of pressure for them to at least show a little bit of BotW2.