We reported on the coming ability of developers to mix XNA and Silverlight programming and this was confirmed today during the MIX11 keynote.
What this means for consumers is much richer apps with fluid 3D graphics within them. In other words, think of the graphics from your Xbox LIVE games and now add that ability to say a GPS app with a 3D rotating globe.
To see what it looks like, see the above demo from a MIX11 session. It should give you an idea of what's coming soon.