Thanks for your questions.
We plan to launch our official Silverlight 3 controls with the forthcoming SP1 of RadControls for Silverlight. It is due in August.
As for your other questions - we are still researching on how we can extend our RadEditor for Silverlight control. It is definitely a matter to decide and we will definitely announce our decision once we have it. We have not planned a development on a PropertyGrid control, however, we can assist you in supporting your existing implementation and help you resolve the problems (challenges) you face with our RadGridView control.
the Telerik team