Typically, Apple tends to stick to some sort of schedule for the release of iOS and iPadOS. Both operating systems usually get released the same week or the week after the September iPhone event.
However, Apple is reported to having to delay the release of iPadOS 16 later this year, due to issues with Stage Manager as beta testers have reported this feature to be somewhat buggy. The feature makes multitasking more seamless and is only coming to M1 iPads. Some reviewers have mentioned the feature and said it still needs work.
This news comes from Mark Gurman at Bloomberg who reported that iPadOS 16 is getting pushed back from a September to October release instead. Bloomberg also mentioned that this delay will allow Apple to focus on iOS 16 and make sure it is ready for prime time.
macOS Ventura is still due to be released in October and Stage Manager is also coming to the Mac, to help make multitasking and window management easier.