There's a new calendar working group at the IETF. This group's purpose is to simplify and improve the iCalendar standards. Complexity of the standards, and different interpretations in different vendors' implementations have been significant inhibitors to interoperability. This group's charter is specifically designed to solve those problems.
I hope that all interested parties contribute to the WG and, of course, continue to work with the Calendaring and Scheduling Consortium. Once interoperability is achieved, and calendar services seem as plumbing-like as electronic mail, there's no telling what new capabilities we'll have!