ちゃんと Terminated が送られてくる
see http://doc.akka.io/docs/akka/2.2.0/general/supervision.html#what-lifecycle-monitoring-means
One important property is that the message will be delivered irrespective of the order in which the monitoring request and target’s termination occur, i.e. you still get the message even if at the time of registration the target is already dead.