Apple sent out notices to application developers, which stated the need for mandatory support programs of the Super Retina display of the iPhone X.
The requirement will come into force in April this year. After that, all applications that are sent for review to the App Store must conform to the requirement.
Thus, if developers want their new or updated program appeared in the App Store, it must support a display with a cut in the top. In addition, new applications should be based on the iOS SDK 11.
Apple, however, in its notice did not specify the deadline for updating existing applications. Only that new applications should comply with the new requirements from April.