It looks like the Perth Mint Platinum Platypus is becoming extinct in 2017, to be replaced by a 1oz Platinum Kangaroo starting in 2018. Wording suggests the design is the same as the silver kangaroo, hopefully the premiums are more in line with their 1oz gold coins:
https://www.legislation.gov.au/Details/F2017L00159/Explanatory Statement/Text
https://www.legislation.gov.au/Details/F2017L00159/Explanatory Statement/Text