After a person has downloaded an ics feed, will their calendars be populated with future events?

Some user-to-user support: The file downloaded contains a pointer to the iCal feed on your website, not a copy of the events. How frequently the user's calendar is populated with new events/dates depends on the settings in their calendar programme—it might check your feed every 5 minutes, every hour, every day, or every week. But yes, as long as they remain subscribed, they will get the new events automatically into their calendar. That's what makes an iCal feed such a beautiful beautiful thing! :)

but the ical file has every event in it. and not a pointer to the ical feed.
for example http://www.registrar.fas.harvard.edu/calendar/ical/2012-10-24--2013-10-24/calendar.ics?field_event_audience_tid=16&field_event_topic_tid=All

BEGIN:VEVENT
UID:calendar.91789.field_date.0
SUMMARY:Winter Recess begins
DTSTAMP:20121024T183558Z
DTSTART;VALUE=DATE:20121222
DTEND;VALUE=DATE:20121223
URL;VALUE=URI:http://www.registrar.fas.harvard.edu/event/winter-recess-begins
DESCRIPTION:Saturday\, Dec 22\, 2012
END:VEVENT
BEGIN:VEVENT
UID:calendar.91790.field_date.0
SUMMARY:Winter Recess ends

As of now, the mechanism for "subscribing" to future updates is entirely dependent upon which calendaring client you use. If your client is pulling the iCal feed directly from the URL published by the View you set up for iCal output, it should be able to pull regular updates from your Drupal site. If you downloaded the .ics file and loaded it into your calendar, then the calendar client has no way of knowing where to go to get updates.

babbage: Do you know how the "pointer to the iCal feed on your website" is supposed to be implemented in the VCALENDAR object? I can't find anything like that in the spec.

The 7.x-2.x branch added the LAST-MODIFIED field to VEVENTs, so if an event changes on your site, your calendar client can tell if it needs to update that event itself.

I'll look into making subscription more robust, which may relate to the work I do for #1529506: webcal:// Support.

I'm closing this issue as part of some spring cleaning. If this has not, in fact, been solved, please re-open the issue with an explanation.