While the extreme slowness of updating the Mac Pro line is concerning (Thunderbolt is *greatly* missed), Apple is updating them in 2013, so there's hope that the line will continue, even if it's obviously not the highest priority.
http://www.forbes.com/sites/connieguglielmo/2012/06/12/apple-says-new-models-designs-for-imac-mac-pro-in-works-due-in-2013/