WhatsApp is currently testing feature that will allow users to retain all their conversation after switching to a new phone number. Something that is currently impossible due to the way user accounts are registered.
The feature is being tested in WhatsApp Beta 2.18.97 – which is available on the Google Play Store. Through it, users will be able to attempt transfer their entire WhatsApp account to a new phone number on the same phone. As a result, conversation histories will be ported over to what is technically a new account; groups will also be retained releasing the user from having to rejoin old chats.
Also important is that the app will inform others that the user has a new phone number. Possibly preventing confusion from setting in.
There’s also a level of control over who gets to see the new number notification. Allowing people to block out certain individuals that may have prompted the number change in the first place.
For now, the test is only running on Android devices. Which has been WhatsApp’s modus operandi for a while now. There’s no telling how soon the feature will be released to the general public; seeing that it is unlikely to be commonly used.