A while ago, Microsoft stopped developing new features and UI for Windows 10 Mobile but the company still releases new cumulative updates for the operating system every month on Patch Tuesday.
On December 10, 2019, Microsoft will end support for Windows 10 Mobile version 1709 which was released in October 2017.
Microsoft has already ended support for Windows 10 Mobile version 1511 which shipped in November of 2015. Windows 10 Mobile Anniversary Update support has been discontinued as well and Windows 10 Mobile Creators Update mainstream support ended on October 9, 2018. The Enterprise and Education are still supposed as they receive an additional 6 months of support.
The last and latest version of Windows 10 Mobile is the Fall Creators Update (version 1709) which was released in October 2017.
According to Microsoft’s Update Cycle page, the support for Windows 10 Mobile Fall Creators Update will end on December 10, 2019.
It means that you will be receiving cumulative updates till December 10, 2019, but things will change after the Redmond giant ends support for its mobile operating system. The platform is likely to function partially after Microsoft ends support and you can continue to use your Windows Phone even after the period but it won’t be serviced.
Once the end of support is reached, there will be no updates security patches for Windows 10 Mobile.