WhatsApp is reportedly working to bring ads to iOS. The Ads are expected to come on Whatsapp by the year 2019. The ads will be shown to the users through the status feature. Android might also soon release the same update.
Whatsapp was acquired by Facebook in 2014 and it further added that Whatsapp will continue to function independently. Mark Zuckerberg already had talks with Brian Acton regarding the ads before the acquisition of the chat platform and he had promised that Whatsapp would remain ad-free.
Brian Acton also recently declared this monetisation of whatsapp as one of the reason for why he left Facebook.