In its present state this is possible but when the engine is changed to use WPF as its backend you'll be presented with another massive effort. Hopefully it will be possible for WPF/E to solve the problem.
WPF?
WPF = Windows Presentation Foundation. Essentially its similar to xgl (I think...) on linux and Core Animation on Macs.
So instead of communicating directly with DirectX as we do now, we communicate with WPF, which offers a much larger range of tools and classes than we can ever hope to have implemented on our own, giving us the ability to make nicer UIs. WPF then communicates with DirectX.
WPF/E = Windows Presentation Foundation Everywhere. It is essentially a stripped-down version of WPF designed to work on PDAs, inside all web-browsers as a plugin etc. Think of it as similar to Adobe Flash.
Sam