WhatsApp on iOS supports voice message transcription since almost a year. It was rolled back to iOS users in May 2023. Apps like Google Messages and Telegram already supports this feature on Android. The feature is free to use in Google Messages and it is kinda paid for telegram users. I think Telegram only allows two voice message transcripts a week if you are not a premium user.

Anyway, WhatsApp is finally catching up with other apps and with the latest beta version of WhatsApp, they started working on it and an APK teardown reveals some strings which hints at this feature. Here are some strings - 

• To enable transcripts, 150mb of new app data will be downloaded.
• Enable
• Read before you listen with transcripts
• "WhatsApp uses your device's speech recognition to provide end-to-end encrypted transcripts. Learn more"
• Turn on transcripts

So according to the strings, it first need to download 150mb of data which will be necessary for it to work. It will use the device's speech recognition system to provide the end-to-end encrypted transcripts which means the feature will not affect the encryption process. 

This option will likely be available under the Settings > Chats, just like on iOS, whenever it is rolled out. This is still in work and may appear for beta users of WhatsApp anytime. I personally didn't have any luck enabling it so there are no screenshots.

For more such leaks you can join my telegram channel - Gapps Flags & Leaks or follow me on Twitter/X