When resuming is not possible with stream management, a hot reconnection is done (stream is restarted but plugins are kept loaded).
For now, we manually handle critical plugins like MAM (XEP-0313) and MUC (XEP-0045), but it would be more generic, maintainable and clean to use specific method like
prepareResume (called before the session is restarted) and
resume (called after session is restarted) so plugins can handle themselves what must be done. The plugin XEP-0198 would call the methods if they exist on all loaded plugins.