I would also suggest WPF as another UI framework to get under your belt, because it does afford some pretty powerful UIs in desktop applications (and most of what can be one in WPF is translatable to Silverlight for webapps).
On the flipside, instead of looking for the next new UI language or technology, I think you may be better served looking at UI from a usability standpoint, and tracking the trends currently making waves.
As an example, one of the paradigm shift I'm seeing in UI development (mostly on the web) is the switch to making important things bigger and less important things smaller - including yes/no buttons in a dialog. I'm still warming up to this idea because it flies in the face of a consistent button look to show users their options.
Instead of providing options in a world today where we are constantly making decisions, the goal of this newer UI look is to breadcrumb the happy path. If the user decides they want to do something different, they can, but the UI is going to make the user put in a little effort and read the fine print.
Another example is flash-highlighting a recent change a person has made (SO does this, but I forget the term used to describe this effect) when coming onto a website.
Lastly, and this is one of my favorites, the shift from an administrative/user view (also mostly in the webapp sphere), to an ad-hoc WYSIWYG editor...Flickr is a prime example of this, where you can change captions on a picture by clicking on the current caption and editing it inline, without the need to go to a separate admin view to edit these values.
Is anyone else seeing trends like these that are interesting and new?