New OSes will drop support for some of the hardware

New releases will support less hardware than current ones.

iOS 17 will be supported on these devices (and, obviously next models):

• iPhone XS and XS Max and newer
• iPhone XR
• iPhone SE (2nd and 3rd gen)

iPadOS 17 will be available:

• iPad mini (5th generation and later)
• iPad (6th generation and later)
• iPad Air (3rd generation and later)
• iPad Pro (all models except 1st-gen 12.9-inch)

watchOS 10 will be land on these watches:

• Apple Watch Series 4
• Apple Watch Series 5
• Apple Watch Series 6
• Apple Watch SE (1st and 2nd gen)
• Apple Watch Series 7
• Apple Watch Series 8
• Apple Watch Ultra

macOS 14 will be supported on these Macs:

• iMac: 2019 and later
• iMac Pro: 2017
• MacBook Air: 2018 and later
• MacBook Pro: 2018 and later
• Mac Pro: 2019 and later
• Mac Studio: 2022 and later
• Mac mini: 2018 and later

References:

• Which iPads support iPadOS 17? Here’s the list …
• iOS 17 drops support for iPhone 8 and X, here are all compatible models
• watchOS 10: These are the Apple Watch models compatible with the update
• Which Macs support macOS 14? Mostly only Apple Silicon models. Here’s the list …