Android Police reports that WhatsApp is testing a feature that would allow you to pin chats, keeping them at the top of the chat list even if you get messages from other users.
To pin a chat, users can tap and hold on the chat, and a pin logo will appear on the top bar along with the delete, mute and archive logos. Users can pin up to three chats, and can easily unpin any of the three chats to add a**ther. Read more...