I haven't adjusted my Turtle format at all in transitioning to 2015.
I suppose am unusual in that I actually prefer Turtles: they are easy for Process Owners to construct and take ownership of, and they are actually a pretty good self-contained job description for Process Owners. There isn't enough modification to the standard that requires a change in what is a document with clear boundaries.
However, one thing I am considering, because I have asked EACH of my Process Owners to do their own Interested Parties analysis and Risk Assessment, is adding extra boxes onto the diagram to represent these. Perhaps they need to be called tarantula diagrams?