Back in June 2017, Apple had revealed the iOS 11 at WWDC event. Apple also claimed that the brand new operating system will be available on September 19 for iPhones, iPads, and iPods with improvements and number of advanced features compared to iOS 10.
iOS 11 will come pre-installed on iPhone X, 8, and 8 plus but it can also be available for older devices. Thus, the users who are planning to stick with their older devices, they can still benefit from the software upgrade. This means iOS 11 is available for 5s and later, all iPad Air and iPod Pro models, iPad Mini 2, iPad 5th generation, and iPod Touch 6th generation.