InfoQ: Dealing with Information Overload and Improving Effectiveness:
by Scott Hanselman
Silverlight is not mentioned, and it is likely to be treated the same. In fact, having "desktop" and "metro" web browser behave differently is a bit strange.
Even more, it appears that limited desktop mode will be available in Windows RT, that is ARM based Windows 8, for tablets.
It is likely that Microsoft marketing has realized that main competitor is Android, and that limiting features may not be best after all...