@DevTeam The updates to the preview voices are published through the Azure updates page and documentation. You can subscribe to the RSS feed on the updates page for regular updates to the service.
Since preview voices can change or be merged, they are offered with supplemental terms and conditions and are available only in specific regions.
Based on my experience, the voice list API should be used to get the available voices for a region and displayed in your application, this API also provides a status field in the response, and you can enable your application to read this field and load the voices separately as GA and Preview. This will allow your customers to try out the new voices as per the preview conditions. If a voice is moved to GA the voice will still be available and if the voice is merged with a different voice or the if the name is changed then you can use the same update to publish in your application and advise your customers accordingly.
I hope this helps!!
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