I was reading up on the new features comming in silverlight 5. And it seems to me that one day we may very well see silverlight running on the XBOX thus completing the trifecta (PCs/XBOX/WF7).
It really makes sense if you think about it. Silverlight is designed to run on almost any pc/mac hardware and with the introduction of xna graphics features in SL5 I'd bet microsoft is planning to make silverlight availible on xbox one day similar to there current xna/xbox setup.