According to WABetainfo, WhatsApp is developing a review tool for voice messages! A new way to listen to voice messages before sending them is currently under development.
After enabling for beta testers the feature that allows to use different playback speeds to listen to voice messages, WhatsApp is now starting to develop another feature for voice messages.
WhatsApp already had a similar feature to review voice messages, but the way to trigger the feature was very cumbersome, for example switching to a different section before sending the voice message.
This new feature (currently under development) will add a new Review button, that you can easily tap to listen to the voice message.