ForApple to discontinue the Mac Pro would be the stupidest move the company ever made. Now I'm not saying they are or aren't, just that it would shoot themselves in the foot by doing so.
Lets face it, Apple products have an image. They are considered "cool" "hip" because they are associated with "creativity" and the creative world...
Yes it was the professional creative users that kept Apple alive during those bleak years, but more than that it was those same customers that made Apple cool for the kids wanting to be them...
First of all: I like the MacPro. I think it needs to be updated. And I hope Apple will continue producing a cool Pro tower.
With that out of the way, there is simply no truth to the insinuation that creative professionals in general needs the MacPro.
An example: In the advertising industry, where I have worked for 16 years, at least 9 out of 10 Macs are not MacPro. Where I work now it is 1 out of 47 to be exact*.
Even our video editors are on iMacs these days. Most of us are on MacBook Pros - mainly since portability is of much higher value to us than even more CPU horsepower (MacBook Pros and iMacs are super-fast).
Most of the professional photographers I work with are also on MacBook Pros or iMacs these days. Same goes for Programmers, Illustrators, Animators, UXers, DJs/VJs, Movie Directors, Fashion Designers, Stylists, Locations Scouts, Casters ... You name it.
There is obviously still a need among 3D people (most that I know are on PCs though), movie editors and other power-hungry people.
But in general I'm pretty sure the creative pro community will stay Apple faithful - even if Apple decides to kill our beloved MacPro.
* Yes, I work at a professional agency. In fact it is one of the worlds largest, constantly award winning, advertising networks.