My name is Todor and I am the product manager of AppBuilder - the part of Telerik Platform responsible for building your apps.
I am happy to say that UWP support is on our road map. However, this is a huge technical challenge and for its successful implementation we depend on Microsoft to a certain degree. In more details, the tooling for building UWP apps has to mature some more and address some issues that are currently preventing us from going forward with this feature.
I'd like to invite you to up-vote the relevant feedback item
to help us prioritize this task.