[mythz]

MSFT strategy is to develop a lightweight, cross-platform .NET runtime that can be hosted on Linux/Windows on Azure - that's where their ROI lies and where their .NET Core investments are focused. Their mobile/cloud approach is about using Xamarin to develop iOS/Android Apps that connect to backend Services hosted on Azure. Although they won't mind if you use Swift or Java to develop native iOS Apps or deploy on Linux - just as long as you host your backend Services on Azure.

There's very little incentive for them to invest in making a cross-platform Desktop UI, most x-plat UI's suck and requires significant resources and offer little return given the most popular UI's are either Web/Mobile - which they've already got covered.

I'd expect the most likely UI for .NET Core is to host a .NET Core runtime with a cross-platform web-based shell using something like Electron or CEF.