Apple unveiled iPadOS 16 in June earlier this year and typically, both iOS and iPadOS 16 get released at the same time, around a week after the new iPhone has been launched. However this year, iOS 16 was released in September but iPadOS 16 was delayed. Apple had pushed the release back due to unforeseen issues with Stage Manager.
Initially, Stage Manager was only going to come to iPads with the M1 chip or greater, but down to optimisations, Apple has been able to bring the new multitasking windowing system for apps to many more iPad Pro models.
iPadOS 16 also bring the Weather app to the iPad for the first time as well as adding the ability to unsend and edit iMessages, plus much more that was added to iOS 16 in September. iPadOS 16 will be available next week on Monday 24th October.