Optus seem to be following other RSPs in offering complimentary speed upgrades for 6 months for those on 50/20 or 100/20. I’m currently on the 50/20 speed speed pack & just received an email informing me that I will be upgraded to the Superfast speed pack (215Mbps Typical Busy Period Download Speed) for the six month period which isn’t bad although I’m not sure what to do with extra speed.. maybe download some linux ISOs ¯_(ツ)_/¯
The Speed Upgrade will appear on your bill as either ‘NBN Speed Pack Home Superfast’ or ‘NBN Speed Pack Home Ultrafast’, with a corresponding credit so you won't be charged extra for it.
NBN Speed Pack Home Superfast = up to 250/25.
NBN Speed Pack Home Ultrafast = up to 1000/50.
Here’s a link to Optus is web page outlining the deal.