In the past few years,
XAML has had its ups and downs. XAML stands for Extensible Application Markup Language, and was introduced by Microsoft in 2008 as part of its Windows Presentation development technology known as Windows Presentation Foundation (WPF).
Today, XAML is primarily used to build WPF, Universal Windows Platform (UWP) applications, and Xamarin Forms. UWP is a technology to build Windows 10 apps that targets any Windows operating system device including PCs, Windows tablets, Surface, Xbox, and HoloLens.
So, we can say, the future of XAML relies on the future of WPF, UWP, and Xamarin.Forms.
Universal Windows Platform
UWP is Microsoft's platform to build apps targeted to all Windows devices. The following graphics show the UWP app universe. Learn more about UWP -
Introduction to UWP >
The popularity of Windows 10 apps has grown rapidly in the past year and it will continue to grow. The Windows 10 operating system is being adapted by more devices each day. Microsoft expects Windows 10 to be installed on one billion devices worldwide.
Watch this video to learn more about the future of XAML.
WPF
Windows Presentation Foundation (WPF) is a fully-mature platform to build Windows client applications. XAML is the core user interface development language for WPF applications. The popularity of WPF may not be growing but it still has its use when building Windows applications.
Xamarin
Mobile apps are everywhere and demand is still growing and will continue to grow. Xamarin can be used to build mobile apps to target all iOS, Android, and Windows platforms using a single language, C#. Many companies are frustrated with writing and maintaining separate code for iOS, Android, and Windows (not really). Xamarin is a choice for developers to have a single code base to target all iOS, Android, and Windows devices.
Microsoft recently acquired Xamarin, a cross-platform mobile app development company and you can see from Google Trends (below), that the popularity of Xamarin has taken off in the past few months.
Recommended Resources
Here is a basic introductory book that will get you going with XAML >>
Programming XAML