In a support document dated January 2, 2019, Microsoft has announced end of life for the last few products that use the Windows Mobile operating system. Most Windows Mobile devices are already considered obsolete. Support for Windows Mobile ends in June for two more device models and in December for the rest.
Nominally, the announcement says that the last two operating system versions will be updated for a few more months, depending on the version. In practice, it is fair to expect that the operating system will not be updated for new security risks unless the potential attack vector is particularly broad and the fix is particularly simple. This announcement marks the definitive end of life for Windows Phone, so any software developer who was thinking of updating an application will be giving up that idea now. Users will continue to use the phones at their own risk for a few more years.
Windows Mobile was a key part of the design philosophy for Windows 10, the current version of the Microsoft Windows operating system. The operating system could continue to be used on desktop computers for ten more years or longer, but eventually, that platform too will be abandoned.