The annual Kusu Pilgrimage is from 9 Oct to 7 Nov 2018. This year, it seems the ferries will continue to go to St John's Island during the period. But parking at Marina South Pier continues to be limited.
blog post for a glimpse into the history behind the island and the pilgrimage.
This year, unlike previous years, according to Island Cruise: The ferry service to St John's island will still be available, with minimal changes to the ferry schedule.
From MPA's notice: during the pilgrimage, the Marina South Pier carpark is closed from 0600hrs-1700hrs. Take public transport or park at the Cruise Centre and walk to the Pier. On weekends and public holidays, there is also a free shuttle between the Meadow carpark (Gardens by the Bay) and the Pier from 0600hrs-1700hrs.