The change is effective January 31, 2020, and, according to Microsoft, cited by The Verge, the Cortana app will disappear in the UK, Australia, Germany, Mexico, China, Spain, Canada, and India.
After January 31st, 2020, the Cortana mobile app on your phone will no longer be supported and there will be an updated version of Microsoft Launcher with Cortana removed.Microsoft
Cortana, however, will get deeper integration with Microsoft 365 productivity apps. In order to achieve this, Microsoft says it has to end support for the Cortana mobile app on Android and iOS.
It’s not sure how this will affect users in the United States. For now, Microsoft says it will continue to work in the U.S., but for how long, that remains a mystery.