As of today, the expiry date remains the extended date, i.e. 31 March 2020.

It does not make any sense if they are talking about ‘activity’ in their terms if they revert back the expiry date to the original. I can book a hotel which allows free cancellation (activity occurs) to stay almost a year later, say late-August 2019. My miles is extended immediately. By August 2019 before I cancel the hotel booking, I may have already exhausted the miles! ^^