Leo's talking about it and having problems finding good and consistent information about it. This is really my bad...I promised I would find time to document what we've done in a much more human readable way but I just haven't had time. Masahide Kanzaki's summary is very cool, though I think slightly out of step with the most recent changes to the schema (and Masahide wasn't happy with those changes).
So this is very much an activity (a taskforce of the Semantic Web Interest Group) that depends on people's interest and enthusiasm, which seems to have petered out at the moment. This has happened before and the mojo of the group always comes back. At the moment though, it's clear that the work is in a state such that people can't easily pick it up and play with it, despite all the good stuff that's out there.
At the same time, the IETF Calsch working group (who created iCalendar and related RFCs) are starting to stir and sort out their priorites for further work. One suggestion is perhaps to simplify iCalendar, something that a lot of our RDF iCal users would like I think.
As to the future....these would be my priorities:

  • stablize (a subset of?) the schema
  • fix up the documentation
  • specify a subset of icalendar/RDF iCalendar that's mostly interoperable and expresses what we want
  • work out how to identify events
  • provide some examples of mixing vocabularies together, espcially GEO, images and RSS 1.0
  • perhaps specify an XML profile of it (using schematron perhaps?)
  • relax and watch as everyone moves to using RDF iCalendar ;)

Update: Dan Connolly has suggested some ways forward.