There is a little more to it than XAML. Skills wise it's not too bad but I have looked into porting some WPF apps to WinRT a while ago and those frameworks looked very differently under the hood despite some superficial similarity. I still don't understand why they need to create all this framework churn. WPF could have been extended to what UWP is now in my opinion.
WPF was XAML v1. Silverlight was XAML v2. UWP has XAML v3. Your skills are still applicable.