Update Release 8 for Autodesk® Revit® 2015 R2 was released yesterday. Subscription customers who have installed the Revit 2015 R2 mid-year update can apply this update if they currently have Update Release 7 for R2 installed, or R2 without any updates. See the full details in the Read Me. A list of the improvements can be found here.
It appears that the same download also works for the "Non-R2" Revit 2015.