Update on April 5:
An anonymous source at MacRumors continues to claim that iOS 17 will continue to support iPhone 8/8 Plus and iPhone X. All devices that support iOS 16 will support iOS 17, including all A11 chipsets.
The article before it was updated
According to MacRumors, iOS 17 and iPadOS 17 will drop support for the iPhone 8, iPhone 8 Plus, iPhone X, first-generation 9.7-inch and 12.9-inch iPad Pro, and fifth-generation iPad.
Thus, the list of supported devices for iOS 17 and iPadOS 17 will be as follows:
iPhone
iPhone 14 Pro & 14 Pro Max
iPhone 14 & 14 Plus
iPhone 13 Pro & 13 Pro Max
iPhone 13 & 13 mini
iPhone 12 Pro & 12 Pro Max
iPhone 12 & 12 mini
iPhone 11 Pro & 11 Pro Max
iPhone 11
iPhone XS & XS Max
iPhone XR
iPhone SE (3rd generation)
iPad Pro
11-in. iPad Pro (4th generation), 12.9-in. iPad Pro (6th generation)
11-in. iPad Pro (3rd generation), 12.9-in. iPad Pro (5th generation)
11-in. iPad Pro (1st and 2nd generations), 12.9-in. iPad Pro (3rd and 4th generations)
10.5-in. iPad Pro (1st generation), 12.9-in. iPad Pro (2nd generation)
iPad
10.9-in. iPad (10th Generation)
10.2-in. iPad (9th generation)
10.2-in. iPad (8th generation)
10.2-in. iPad (7th generation)
iPad (6th generation)
iPad Air
iPad Air (5th Generation)
iPad Air (4th Generation)
iPad Air (3rd generation)
iPad mini
iPad mini (6th generation)
iPad mini (5th generation)
Last year, iOS 16 and iPadOS 16 dropped support for quite a few devices, including the iPhone 6s, iPhone 6s Plus, iPhone 7, iPhone 7 Plus, original iPhone SE, final iPod touch, second-generation iPad Air, and fourth-generation iPad mini.
Apple is expected to announce iOS 17 and iPadOS 17 during its WWDC keynote on June 5.