Finally made it works by "Waiting for state changes".

Inside optionsBuilder:

 // Create a Completer to wait for state changes
 final completer = Completer<Iterable<GooglePlace>>();

 // Subscribe to state changes
 final StreamSubscription subscription = bloc.stream.listen((newState) {
     completer.complete(newState.places);
 });

 try {
   bloc.add(MakeAutocompleteEvent(textEditingValue.text));
   final result = await completer.future;
   return result;
 } finally {
   subscription.cancel();
 }