Dropped
Microsoft finally and irrevocably gives up on WinJS and drops its support. We're not writing anything new with it anymore. New UWP work moves to XAML and C#.
As for what's already written — it gets demoted to Legacy and maintained as-is, since we don't have the resources to rewrite it.
Using
The application prototype written in WinJS for UWP gets the green light. We're moving forward with it.
Assessing
For a new client I pick UWP to build one of the client-facing applications.