WhatsApp will stop working on all smartphones running Windows Phone as of December 31, 2019. The instant messaging application will even disappear from Microsoft's store on that date. To continue using WhatsApp, the last users of Windows 10 Mobile will have to migrate to Android or iOS.

After a final update, which will be deployed on December 10, WhatsApp will no longer work on Windows Phone. A few weeks later, the email application will disappear from the Store. "You will no longer be able to use any Windows Phone operating system after December 31, 2019″ specifies WhatsApp in a release on its website. The few users of Microsoft's mobile OS will therefore have to do without WhatsApp.

Source: Phonandroid.com