This feature is now shipped in the Atlassian Cloud Enterprise Plan The documentation for this feature can be found here: https://support.atlassian.com/provisioning-users/docs/add-identity-providers-to-connect-users/
We made the decision to not bundle security-related features in Standard and Premium product editions. This means customers on either standard or premium can purchase Access if they require our standard security features like SSO and Audit Logging.
Anything that fits into the more Advance category of security features like Multiple Identity Providers will be packaged in our Enterprise edition as we believe this edition is the best fit for those customers.
I know this is not ideal to hear for some customers, but the decision was not made lightly.
Product Manager, Cloud Security