Should i defer balance payment to get gst rate cut benefit

I booked one house in June 2016, for amount say Rs. 50L, and paid Rs 10% of the total value that is 5L on this. I paid 12% GST on 5L. Last week builder sent me final demand note for Rs 45L plus GST at the rate of 12%.

As layman, what I understood from GST council decision on 24th Feb 2019, now 5% GST will be applicable on house. So, should I defer the balance payment ie 45 Lakh till 1st April, so as to get GST cut benefit.