It is not yet clear which voice commands will be available to the user, but considering that it is a conversational generative AI, it is likely that you can use the messenger to answer questions, request improvements to texts, create code and more. What we don't yet know is whether it will be possible to ask Meta IA to compose a text message and send it directly to a specific contact via WhatsApp, for example.
Additionally, the feature should allow users to customize Meta AI's voice in some way, making the assistant more user-friendly. Code snippets indicating the addition of these features were found in Beta version 2.24.18.18 of WhatsApp, available on Google's Play Store. So, voice chat with Meta AI is expected to come to Android first.
There is still no estimate of when these new features will be available in the stable version of WhatsApp, which is the version installed on most smartphones.