The original courseware materials for 6419 only cover 2008, but a good trainer should be able to mention and explain the differences in R2 while he or she is teaching the class.
I don't usually teach Windows Server classes, but I do teach .Net framework development. If I am teaching a course that uses Visual Studio 2008 and the students mention that they will be using Visual Studio 2010, then while I am teaching I point out those
things that are different, or can be done in a better way, in version 2010. I understand that trainers who teach Windows Server expand on their courses in a similar way when their students show interest in R2 versions.