Thanks for reaching out to us, I have checked with the product team again, however, currently there is no plans for Azure Open AI services in Australia (Australia East - Sydney) for GPT 3.5 and GPT 4.
We have forwarded the request for Australia East - Sydney region for product team for reviewing, if you can provide more details of your usage, it may help the request to be stronger.
Please check for what's new in Azure OpenAI Service page for the updates. I hope this helps.
Sorry for any inconvenience.
-Please kindly accept the answer if you feel helpful to support the community, thanks a lot.