WABetaInfo discovered references to a new feature called 'linked devices' that will allow users to send and receive messages from multiple devices including WhatsApp Web, WhatsApp app and even Facebook Portal. This would allow users to chat from a laptop or a second phone without logging out of the primary device. Furthermore, the feature will allow users to use WhatsApp without an internet connection on the primary device. WhatsApp has currently set four devices as the limit and would allow users to sync, chats, messages across the devices.
WABetaInfo also noted that enabling the new linked devices feature will terminate the existing WhatsApp sessions and will force users to create new sessions because of the change in the mirroring technology. They further noted that the feature is in the final phase and should roll out to WhatsApp Beta testers on Android and iOS soon. Unfortunately, there is no word on when the feature will make it to the public. However, you can enrol yourself into WhatsApp iOS or Android beta to gain early access to the feature.
WhatsApp is also planning to allow users to authenticate WhatsApp Web sessions using fingerprint. It will further improve the app's security, especially after the app gets multi-device support.