Made another booking which got cancelled yesterday, and received this in writing:

1. Ticket status can be remain as an open ticket for 760 days from original date of ticket issuance. You may then rebook later once new date is finalised. Kindly contact EK call centre to cancel the booking in advance. There will be no penalty and fare difference to be collected upon rebooking as long as within same region and same cabin. However any different in Taxes will be collected.

This seems to be consistent with earlier posts on no fare difference being charged.