How is this icalendar stream going to be propagated to the clients ?
If it is just an ics file stored on some web server that calendar client subscribe to using HTTP GET, then clients will typically poll for changes in the file. Events which are no longer part of that stream will implicitly disappear.
If the iCalendar stream is going to be used by clients in some other way (e.g. via email), please specify how.
In any case, having a single stream with the same event (same UID) multiple times in different state is not the way to propagate changes.