Developers rejoice - you've got some new tools in your arsenal, for the next time you hit the keyboard. Microsoft has officially introduced XAML Standard and .NET Standard 2.0. XAML standard seeks to be a "standards-based effort to unify XAML dialects across XAML based technologies such as UWP and Xamarin.Forms," whereas .NET Standard 2.0 will be "a large set of .NET’s 'greatest hits'" mixed into .NET Standard, making for a better version of .NET Standard molded by community feedback.
XAML Standard is hoping to available "later this year," and will be receiving the same kind of post-launch support that you've come to expect, including support with Xamarin.Forms and UWP. Those who are more interested in .NET Standard 2.0 shouldn't have to wait very long, but Microsoft hasn't offered any particulars on just when it will be launching. You can stay up to date with the latest builds of .NET Standard through the .NET Standard GitHub page, where the developers are actively answering questions and helping developers.