WhatsApp is reportedly working on allowing users the option to hide or disable the visibility of their "Last Seen" status to certain contacts, according to WABetaInfo.
WhatsApp Last Seen Settings

Source: WABetaInfo
This featue comes as a part of WhatsApp's privacy push as the Facebook-owned app seeks to give users a great level of control over their accounts
The "Last Seen" status is a feature that allows other users to know when the last time you were active on the app. With this update, the messaging giant rolled out a parameter for "Last Seen" feature dubbed as "My Contacts Except...". However, based on the provided screenshot, if you block someone from viewing your 'Last Seen' status you won't be able to see theirs in return.
According to the source, this option will also apply to other privacy settings as well, such as “profile picture” and “about”.
WhatsApp and Privacy Fines
Last week, Ireland's Data Privacy Watchdog imposed a hefty $266 million record fine on the app for sharing data with other Facebook-owned products.