Apparently Apple product development has been taking cues from Monty Python, declaring the Mac Pro is not dead, it's just resting. A new Mac Pro is coming although we'll have to wait till 2018 when a new design, that is more easily upgradable, will debut. It's a rare admission, I think, of an instance where elegant design has gotten in the way of function by Jony Ives' team.
The new model, which Apple VP Phil Schiller, says is "completely rethought", will be more easily upgraded he told Daring Fireball's John Gruber.
Gruber also learned that new iMacs will be coming this year and that Apple is working on a new display, to replace the retired Cinema Display. The update to the iMacs will be interesting as the amount of processing grunt and the display quality of the 5K iMac means Mac users looking for a high-end experience have probably moved on from the Mac Pro.
Getting them back will be a challenge.
For IT professionals, I think your best bet for buying a high-powered, affordable desktop system that can be upgraded is a Windows 10 box - something that has been the case for a long time if you aren't wed to Apple's design.