The GSTR 3B filing due date for May 2020 was 20th June 2020. However, for taxpayers with an aggregate turnover up to 5 crore rupees, the due date was extended to September 2020. For those with a turnover exceeding 5 crore rupees, the due date remained 27th June 2020, as confirmed by notification no. 36/2020-central tax.
Due date is 27th June. Nothing has changed for taxpayers having a t/o above 5 crores even after 40th gst council meet. You can refer notification no. 36/2020-central tax