My thinking is that you could register an app to 2 event sources.
- The first event source will handle the general notifications that an app should receive, whether a user is logged-in or not.
- The second event source will handle the notifications for logged-in users.
When the app launches, subscribe to the first event source.
When the user decides to log-in, subscribe to the second event.
You should allow the user to unsubscribe from both if s/he so chooses, as well.
Additional information:
- IBM Worklight 6.1 Information Center: search for "push notifications"
- Push Notifications training module