For those not taking advantage of the myriad of “free” 
iPhone 15 offers in the market, iOS 17 is now available for your current iPhone (requires iPhone SE2 or newer or iPhone XR, XS or newer).
Here’s one review from a couple of former Macworld editors:
Associated operating system updates for additional Apple devices (iPadOS, watchOS and tvOS for iPad, Apple Watch and Apple TV respectively are also available).