Yesterday (2/15), Apple sent a notice to developers with an update to their evaluation terms new apps.
According to the statement, as of April 2018, all apps sent for evaluation from the App Store will necessarily have to be created using the iOS 11 SDK, which can be found in Xcode 9 or later.
Apple also claims that all new apps designed for the iPhone, even those that are universal, should have screen support Super Retina HD iPhone X. That is, it will be necessary to support the resolution of 1125 × 2436 pixels for the vertical orientation and 2436 × 1125 pixels for the horizontal, in addition to having to respect the safe areas and adaptive layouts. Another future requirement is iPhone X's own screenshots.
These requirements are meant to, in addition to making sure that apps work well on Ma?s newest device, make developers actually use the features and new technologies that came with iOS 11, like Core ML, ARKit, the new camera APIs, SiriKit and more.
But as Apple normally does, it will give the developers some time to adapt, since the requirements will only start in April. And in relation to apps created with previous SDKs and which are already on the App Store, it is possible that Ma will continue to allow them to remain in the store only for a while, and then require them to be updated to the newest SDK as well.
So, if you are a developer and have not yet entered these parameters, better do it soon so that there is no problem later.