Did you read the comments? Many questions were asked there and answered by the author.
I did, and the full response to that comment was more interesting -

I'm not aware of any plans to provide a cross-platform UI framework, if that's what you're asking for.

In general, I don't think we believe in using the exact same bits on all platforms. From personal experience I'd say the goal of any successful cross-platform strategy is maximizing sharing while not compromising the experience due towards the lowest common denominator.

So I'd say: think of your app as a burger, representing the layering. The bottom bun will require OS specific implementations, but we'll probably provide a good chunk of it. The top layer (UI) is also very likely to require leveraging OS/experience specific functionality. The beefy part in the middle represents your business logic and you should make sure you can share most of it across all platforms. OS specific concepts should be either pushed down or up (via inversion of control).
His logic makes complete sense to me, and if i can create a solution with basically a shared back end and business logic layer and then just have separate projects for the various front ends that would be fantastic, it is a more sensible and better goal than think there will be 1 UI to rule them all.

The thing is none of us know exactly where this will go, it is not that black and white. There is a lot up in the air, a lot in progress so we cant fully realise the shape of things, and a lot of positive sounding stuff (well to me, obviously not to you )


One further reply by the author in those comments

So basically WPF will die together with the old .NET Framework that will eventually be superseded by .NET Core?

No. The .NET Framework doesn't die -- it simply versions slower. You can think of .NET Core as the faster moving younger brother.
So in truth there is still more going on than simply maintenance.
Admit it, really your just Jealous of all the current attention on .Net