The iPod touch was discontinued this week, which may be an indication that as many as nine other devices are about to lose support for Apple's upcoming operating systems.
All of the same devices are supported, with the exception of the first-generation iPad Pro.
The decision about which device to use is likely to be based on the memory of the device. All devices with less than 2GB of memory were dropped by Apple. The first-generation iPad Air, iPad mini 2, iPad mini 3, and sixth-generation iPod touch were wiped out. Even though the iPad mini 4 has the A8 chip, it has continued to be supported by the rest of the operating system.
Nine devices with the A9 and A10 Fusion chips could lose support if Apple requires 3 gigabytes of memory. When Apple drops support for older devices, the A10 Fusion chip in the iPhone 7 Plus and seventh-generation iPad will likely retain support.
There is no evidence to suggest that Apple will support the seventh-generation iPod touch, a device with 2 gigabytes of memory, simply because it was sold until now. The sixth-generation iPod touch was discontinued by Apple in May of 2019. The seventh-generation iPod touch could be discontinued in May 2022, just months after it is removed from support for Apple's mobile operating system. Even though the Apple Watch Series 3 is still on sale, watchOS 9 will no longer support it later this year, according to Apple analyst Ming-Chi Kuo.
The following devices could be supported if Apple made 3GB of memory a requirement.
There is an operating system for the iPad
iPadOS is the operating system for the iPad.
This would make the first-generation iPad Pro the oldest supported iPad model. Apple could look to avoid confusion about why the iPhone 7 Plus is supported while the iPhone 7 is not by dropping support for both devices at the same time.
All of the same devices could be supported by both iPadOS 16 and iOS 16. It seems like it's just a matter of time before Apple drops support for older devices. It seems likely that the above devices will retain support when that happens.
The Worldwide Developers Conference will feature major updates to all of Apple's operating systems in June of 2022.