According to the Israeli site The Verifier, the iOS 14 will now be compatible with several iPhone and iPod Touch models that can run iOS 13. The Verifier says that it got the compatibility data from a trusted source from the system development process. The compatibility data was found in a leaked version of the iOS 14.
iOS 14 supported devices
iOS 14 supported devices are the iPhone SE (2020), iPhone SE (2016), iPhone 11 Pro Max, iPhone 11, iPhone XS, iPhone 11 Pro, iPhone XS Max, iPhone X, iPhone XR, iPhone 7 and 7 Plus, iPhone 8 and iPhone 8 Plus, iPhone 6s and 6s Plus and the 7th-generation iPod touch.
The Verifier also says that Apple often offers software updates for the device for the next four or five years after releasing it. Currently, there is nothing about the iOS 14 supporting iPad versions which run iOS 13.
It is expected the compatibility will be for the 3rd generation iPad Air, iPad Air 2, the 5th, 6th, and 7th Generation iPads, iPad Mini 4 and 5, and also all the iPad Pro models.
Apple will unveil the iOS 14 in the upcoming WWDC event that will start on June 22.