It is safe to say that the Windows 10 Mobile platform is dead, although it has recently received a new feature. There are no new phones and smartphone manufacturers are not even working on them, but Microsoft is aware of the smartphone market and has been doing a lot of work in the labs.
You have probably heard about the special Windows 10 version that runs on Snapdragon 835 processor, but the Redmond-based company has bigger plans for the mobile platform. Citing inside sources, Zac Bowden from Windows Central, wrote that Windows Mobile 10 development has been moved away from the rest of Windows 10. Microsoft's next mobile device will be running an OS that is known as Andromeda OS. The "feature2" branch won't be working on future updates, but will instead provide Windows 10 Mobile devices with bug fixes, security updates, and new Enterprise specific features through 2018.
Andromeda is a version of Windows that will be able to run on any device, including phones, tablets, and desktops, thanks to its modular design. Not much is known about the OS, but Microsoft hopes to release it sometime in 2018.