Same as WPF Feature request...
Due to the radically decreased interest in Silverlight we decided to considerably reduce the efforts we invest in any new features or new components in our UI for Silverlight offering. After numerous conversations with some of our clients we confirmed that our product is mature enough and almost feature complete and can be used as is for most of the scenarios out there. That is why we took the hard decision to invest only in maintenance (fixes sent with regular releases) of the existing UI for Silverlight functionality and controls.