IPv6 is getting fairly widely deployed on mobile networks. A server-less push mechanism could be designed using it.
If either Google or apple adopted this mechanism for push, mobile networks would adopt ipv6
If either Google or apple adopted this mechanism for push, mobile networks would adopt ipv6
This would still require some cooperation from Apple, for the OS to receive the notifications and dispatch them when the app is not running. A long time ago, when there was no outrageously dominant players, the Internet industry would have produced an open communication protocol for this use case. Using the same protocol and the same notification server for both Android and iOS would be nice. Sadly, this is unlikely in today's Internet.