Surprisingly, the announcement was made on the official Google Drive blog. This is surprising mostly because WhatsApp is owned by Facebook, and Facebook and Google don't tend to partner on... well, anything really. According to the blog post, no one likes to have their memories stuck on a phone, so WhatsApp is adding the option to backup and restore your chat history, voice messages, photos, and videos.
Google says the feature will be hitting the Android version of the WhatsApp app today, but unfortunately, the post also notes that the feature will be "rolling out over the next few months", which is not a great phrase to see. Any software feature rollout that takes more than a couple weeks is troubling as far as we're concerned.
The post doesn't specifically mention the iOS version of WhatsApp, but the feature will be using the Google Drive API for functionality, and there is a Drive API for iOS as well. WhatsApp tends to like to have feature parity all around, so we would expect the backup option to hit iOS. In the meantime, just check your settings menu every once in a while to see if you've got the update.
source: Google Drive Blog