"The most recent WhatsApp Android client release includes support for the TextSecure encryption protocol, and billions of encrypted messages are being exchanged daily. The WhatsApp Android client does not yet support encrypted messaging for group chat or media messages, but we'll be rolling out support for those next, in addition to support for more client platforms. We'll also be surfacing options for key verification in clients as the protocol integrations are completed."
This was in 18 Nov 2014. The latest announcement from last month was:
"Over the past year, we've been progressively rolling out Signal Protocol support for all WhatsApp communication across all WhatsApp clients. This includes chats, group chats, attachments, voice notes, and voice calls across Android, iPhone, Windows Phone, Nokia S40, Nokia S60, Blackberry, and BB10.
