WhatsApp is testing a feature that would make it easy for you to notify your contacts about a change in your number with the new change number feature.
The development has been spotted by WABetaInfo, which says the new feature is a part of WhatsApp beta version 2.17.130 for Windows Phone and Windows 10 Mobile.
You will be required to enable this feature, as it would be disabled by default. Your contacts as well as your chat groups would be notified about the change in your number.
Currently, if you change your phone number in WhatsApp, you will have to go through a long process that would involve inserting a new SIM, then going to your WhatApp account and changing the number. However, through this process, your contacts will not be individually informed about the change in number, and only the participants of group chats you are a member of would be able to view the change.
Separately, WhatsApp has introduced several new changes for the Live Location feature in WhatsApp beta version 2.17.150 for Android users. WhatsApp beta for Android 2.17.151 allows you to add a comment for the shared live location, in both individual chats and group chats.