No assumptions, only guesses.
I think that it could go on sale tomorrow. Releases often happen on Fridays, and even if they are intentionally trying to keep it off the streets until after the iPhone event, taking orders tomorrow will still mean that at best it would start arriving in people’s hands around the same time as the event, so I don’t see a reason to wait any longer than that given that by the end of next week they will likely be dealing with iPhone preorders.
That’s all just guessing though.
I would think so as well especially if only to prevent their store from being slammed with orders.
Imagine if both iPad Air 4 and iPhone 12's are available for pre-order right after the announcement on Tuesday? That might bring the site to a crawl!