The three apps would remain separate but their infrastructure behind the scenes would be the same. In future, a Messenger user would be able to communicate directly with someone who has only a Whatsapp account.
The work to merge the three elements has already begun and is expected to be completed by the end of 2019 or early next year.
This would mean that after Facebook is done with the integration a single user profile can be used for the different apps to better target ads. This would also mean that data would likely be shared between the apps to make it easier for the company to track user activites.
All the apps will also get end-to-end encryption which would sheild people outside of the conversation from reading it.
Facebook estimates 2.6 billion people total now use Facebook, WhatsApp, Instagram or Messenger each month, according to its most recent earnings report. In addition, more than 2 billion people use at least one of these Facebook-owned apps each day on average.
WhatsApp was acquired by Facebook in 2014, and its CEO and co-founder Jan Koum left the company in May 2018. Koum reportedly decided to resign after disagreeing with Facebook over its approach to personal data and encryption.
In October, Instagram co-founders Kevin Systrom and Mike Krieger left Facebook after reportedly clashing with CEO Mark Zuckerberg over the direction of the photo sharing app. Instagram was acquired by Facebook in 2012.