Xamarin.Forms is cool but still doesn't work on Linux so it seems the same story as XAML to me - cool but of little use, unlike to HTML which is less cool but absolutely useful as it works everywhere. JavaFX - doesn't work on mobiles/tablets (there was a prototype in 2011, seemingly abandoned), sadly it seems to be about as dead as Flash and Silverlight now. As for QML - search results suggest it works everywhere but still hardly a popular choice for some reason, worth taking a closer look perhaps (but I still doubt it can compare to HTML as using Qt means producing binary builds for every platform to support AFAIK).
JavaFX also follows the same design ideas.
And there is QML as well.