Perhaps I was reading too literally “Older products not listed are not compatible with Mac OS X Mavericks”. I was interpreting that as “Cubase 6.5 will not run on Mavericks.”
Thank you guys for making the world make sense again. 
My fairly modest tests (audio/midi projects with no third party plugins or external hardware) suggest that Cubase 6.5 is compatible with Mavericks.
J