From Apple's perspective, the beauty of recorded presentations vs. live events (e.g. WWDC 2020), is that they can just drop the announcement/recorded presentation and update the store whenever they want. There is no need for an invite to be sent out days or weeks in advance, and generally speaking, we know Apple likes to give us as little info as possible until a product is ready to launch. If they had it their way, we would never be able to guesstimate when software or product releases were likely to happen. Different from WWDC where there were virtual sessions, there isn't even a level of personal interaction that will take place with the remaining product announcements. It's just a recorded product announcement, or basically a glorified advertisement, meaning Apple has even more freedom over scheduling them. Apple likely already has these recorded and ready for the public.
How does this relate to iOS 14? Even if there is a product announcement next week on 9/8, which is still feasible given the above, the products won't be available for pre-order or shipping until the following Friday at the earliest (my best guess, based on prior trends). This means we could see beta 7 tomorrow or early next week, which is really just the GM with the "a" on the build. I think we're due for a beta between now and early next week, since we're now on the weekly train, and we haven't received one in over a week at this point. We could then receive the GM the following Monday (9/14), and public release on 9/18. This is roughly consistent with prior years too, noting that this year has been anything but ordinary...
Seeing as at this point the rumors seem to indicate the iPhone is delayed, if the Apple Watch and iPad are delayed too, then all of iOS 14 could be delayed as well. Seeing as we're only on beta 6, and WWDC was later than normal this year, perhaps everything is delayed. But given new hardware drives sales leading up to Apple's holiday quarter, and the iPhone is potentially delayed, they're incentivized to not hold back products (e.g. Watch and iPad) if they're available to be sold. So unless hardware other than the iPhone is also delayed, I think the above timing makes sense for GM and public release.