While Microsoft and Google are both putting on developer events this week, Apple has a bit of developer news to share as well. It announced today that beginning in July, all iOS app updates must be built using the iOS 11 SDK, and they must support the Super Retina Display of the iPhone X.
Apple points out that with the iOS 11 SDK, apps can deliver "more intelligent, unified, and immersive experiences with Core ML, ARKit, new camera APIs, new SiriKit domains, Apple Music integration, drag and drop for iPad, and more." And while there is more functionality with iOS 11, it does mean that older devices get left behind.
Of course, between now and July is WWDC in June, where Apple will announce iOS 12. This is when we'll find out what Apple has planned next, and what devices will be left behind after the next major update. As it stands, iOS 11 is supported on the iPhone 5s and higher, so it seems likely that iOS 12 will start with the iPhone 6.