According to WABetaInfo, some beta testers can already use eight emoji reactions:
The response selection should appear after viewing the status and swiping up. If someone replies to your status update, the emoji will be sent to you as a message. This is reminiscent of the mechanics of Instagram (*Belonging to Meta, which is recognized as an extremist organization and banned in the Russian Federation). If you reply to someone’s story with an emoji, they’ll get a direct notification.
It is not yet clear when the new WhatsApp feature will come to the stable version.
Source: Ferra