At WWDC 2015 we announced that iOS 9 will support IPv6-only network services. All apps submitted to the App Store must support IPv6 starting in early 2016. To make sure your app is compatible, use the networking frameworks (e.g., “NSURLSession”), avoid use of IPv4-specific APIs, and avoid hard-coded IP addresses. Before submitting your app, test for compatibility.

To learn more, read Supporting IPv6 DNS64/NAT64 Networks and watch Your App and Next Generation Networks.