WhatsApp was rumoured to be testing a new feature on its iPhone beta version that allowed users to revoke or edit messages you have already sent to other contacts. It seems the feature is being tested on the Android beta app as well - though regular users cannot access it right now.
The edit sent message and revoke/ recall message features have reportedly shown up in beta versions of WhatsApp for Android - though they are disabled by default, meaning that you will have to turn it on manually on a rooted phone. As per @WABetaInfo, which tracks beta releases of the app and shared images showing the upcoming feature on Android, the WhatsApp for Android versions 2.17.25 and 2.17.26 have the new edit and revoke feature, respectively.
Apart from edit option, as we mentioned, WhatsApp for Android users will also get a revoke option which will mean that the sent message never existed. The upcoming WhatsApp feature to edit or revoke sent message will work by long pressing a sent message. However, this WhatsApp feature to revoke and edit sent messages will probably work only in the case if the recipient hasn't seen the message from the sender. Currently, WhatsApp lets users delete messages on the device level and the deleted messages remain visible to the recipient.
Unfortunately, there is no word when the new revoke or edit sent messages features will be available for Android users.
WhatsApp for iPhone received an update recently that added many nifty features for users. The changelog included increased the WhatsApp photo and video sharing limit to 30 at one go, a redesigned and more useful Storage Usage screen, and the ability to queue messages - a feature that has been available on Android for quite some time now.