At some point in the (unspecified) future you should be able to move and resize the stock UIs we've given you. This does not mean create your own UIs or introduce real-time scaling of existing UIs (i.e making the LFF panel wider by click and dragging the mouse on the panel edge.)
At some point in the (way unspecified) future, we'd like to be be able to allow you to specify your own UIs and intercept the events we're sending to our UIs in game so that you can specify functionality on your UIs.
At some point in the (way way unspecified) future, we'd like to be able to allow you to specify your own events and commands similar to WoW to implement all kinds of cool UI features.