xMac, Mac Mini Pro, or iMac Pro? Either way you spell it I am sure the Mac Pro of 2013 will not be as highly expandable as the 2010,2009 and earlier. While the Mac Pro might survive, it will be a totally different design and possibly crippled beyond belief.
Again, speculation.. but seeing Apple's interests and directions of where it wants to go.. iToys and watches + Apple TV I don't see much enthusiasm by Apple to be all hoopla over a Mac Pro update.
We will have to see.. until then, my 6-core keeps humming along..