According to this announcement, the right version of Blend to use for Silverlight 5 development is Blend Preview for Silverlight 5, but that expired a while ago. I was using the Blend + SketchFlow Preview for Microsoft Visual Studio 2012 since, but that expired today.
It seems that not only is there still no version of Expression Blend released that supports Silverlight 5, but the two previews that do have both expired.
Does anybody know about a workaround or anything I have overlooked?