06 April 2021
WhatsApp appears to be bringing the animated stickers support on its app, the existence of which was, at least, visible on Android for a short period. As discovered by WABetaInfo, the WhatsApp beta v126.96.36.199 enabled the support for animated stickers but later on, it got disappeared in v188.8.131.52.
Nonetheless, its brief existence on the app has shown how they are going to look. As pointed out by WABetaInfo and AndroidPolice, the stickers only animate once and stop. The source mentions that currently, it is unknown if WhatsApp will decide to allow looping them. You will only be able to see the animation if someone sends you the animated sticker first. Once someone sends you an animated sticker, you will be able to access five animated sticker packs - Rico's Sweet Life, Moody Foodies, Chummy Chum Chums, Playful Piyomaru, and Bright Days.
As AndridPolice points out the looping of animation can be seen indefinitely in built-in WhatsApp picker, though.
WhatsApp is bringing the animated stickers very late. Its competitors like Telegram and Gboard have had this feature for a long time now.
As mentioned earlier, the new animated stickers feature disappears in 194.9 version, so if you wish to keep it then disable the automatic updates. But WhatsApp must be making some changes around it before making it available to everyone, so just remember that the one which is available now could be in its most unstable form.
The beta version 184.108.40.206 is available on APKMirror.