Hi Lucas,
At this point the feature is not scheduled for implementation and I am unable to say when it might be available. I advise you to subscribe to this item in order to be notified about any changes of the status.
As to the fact that you are using Silverlight, most of our controls including RadImageEditor share a common code base between their WPF and Silverlight versions. That said, when we start working on this feature we will add it for both technologies.