Yes, google developer console changed it’s Google Cloud Messaging API to Firebase Cloud Messaging. I guess now onwards we have to use Firebase Cloud Messaging to send push notifications, database operation, etc.
Many of articles not updated to Firebase Cloud Messaging implementation.
We hope @ankushagg93 will update his article very soon because this is a nice resource to follow as I thought.
Though it is not so much difficult process to create a project in Firebase Cloud Messaging for push notification.
I sharing you a link which involves the use of Cordova fcm push plugin. The link not involves thorough steps but helps in setup a little project.
https://github.com/edismooth/ionic2-firebase
or
http://stackoverflow.com/questions/37653251/firebase-cloud-messaging-with-ionic-app
And below here is the repository of Google Firebase Cloud Messaging Cordova Push Plugin https://github.com/fechanique/cordova-plugin-fcm.