Since Q2 2010 inclusive, all new controls will be made for Silverlight 4. We will continue to provide bugfixes in the form of internal builds for Silverlight 3, but there will be no new features or controls for that platform.
the Telerik team
Do you want to have your say when we set our development plans? Do you want to know when a feature you care about is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items