Yes, we will have scaling events ...
There is since yesterday an updated version (to be included in OpenACS 5.10.1) which has an additional parameter "ClusterAutodeleteInterval" (default 2m) to perform an automatic cleanup for dynamic cluster nodes after the specified time of missing reachability.
We can also consider a "disconnect_request" in analogy to the "join_request", which could be automatically issued, when a dynamic cluster node shuts down gracefully. This would not be a full replacement of the auto-delete mechanism described above.