French reseller France Systèmes claims in its latest newsletter that a replacement will be released this spring and goes on to say that it has been informed of the update by Apple. Unfortunately, there is no information regarding hardware, but support for USB 3, Thunderbolt and Fusion Drives (i.e., hard disks made up of solid state disks and traditional spinning disks) would be expected as a minimum.
Many professional users have been waiting three years to upgrade their existing Mac Pro and some have been forced to turn to premium PC products, such as HP's range of professional workstations in order to keep up with the pace of professional software development.
Apple hasn't released an official statement regarding when the Mac Pro is to be refreshed other than to indicate that it will happen at some point in 2013. As it stands, Apple will cease shipping new Mac Pro units to EU countries from March 1, but retailers and resellers will still be allowed, under EU law to sell their existing stocks.