API Availability and Opt Out Flag

Hello  - I have two questions which I continue to Struggle with

Can I confirm that the the availability of Stream APIs is currently looking like Q2 CY2020? 

How can I ensure our tenant is not automatically transitioned before the Stream API is available? 

There is talk of an opt out flag to ensure migration doesn't happen without our say so, but I cannot see anything that I need to set in our tenant. 

https://docs.microsoft.com/en-gb/stream/migrate-from-office-365