With iOS 15, the new iOS update will probably work on iPhone 7 and later devices. That means the iPhone 6s, iPhone 6s Plus and the original iPhone SE won’t work with iOS 15.
If the information is correct, then these iPhones will work with iOS 15:
*iPhone 7
*iPhone 7 Plus
*iphone 8
*iPhone 8 Plus
*iPhone X
*iPhone XR
*iPhone Xs
*iPhone Xs Max
*iPhone 11
*iPhone 11 Pro
*iPhone 11 Pro Max
*iPhone SE (2020)
*iPhone 12
*iPhone 12 mini
*iPhone 12 Pro
*iPhone 12 Pro Max
iOS Beta version for developers
If you're a developer, you'll be able to get your hands on the iOS 15 developer beta whenever the next iOS version is released. You'll have to wait until July for the public beta of iOS 15. Apple will release iOS 15 later this year, as it did last year. This typically occurs in September. That is the time when Apple will unveil the new iPhone. Once iOS 15 is available to download this fall, you will be able to download the update by going to the Settings app>General>Software update.