HTML 5 offers a great support of what Silverlight have been doing since few years. There has been a lot of questions around What will be future of silverlight after HTML 5 comes in full swing. I found a very nice article of Brad Becker talking about future of Silverlight. It can be seen by clicking here.
If you have any more questions, I would reckonned to attend the conference (online) of Scott Guthrie by clicking here