To those claiming the nMP isn't a workstation, please let me know which apps in OSX (OSX Only) benefits from dual cpu or quad gpu?
Do the nMP/osx is used for protein folding, or high frequency trading, or something heavier than Arithmetica or video editing, and of course 3D rendering.
Few pro's on OSX are concerned about a 2nd cpu, and while is somewhat valid to cry for CUDA we should recognize CUDA as the evil closed GPGPU platform we need to destroy with OpenCL, and actually the nMP is up for all the current OSX applications, and while don't offer the best 3D rendering performance it's true many pros actually rent by hours a Renderfarm For that (also those with more powerful hw use to rent gpu time when they need an final rendering).
So I think Apple is selling the workstation that OSX users need (at least at launch, as current the nMP is outdated).
A mac pro is an studio machine not an industrial Bulldozer, for those exists multi cpu workstation, compute severs and so on.
About market decline, it's has more related to delay on sensitive updates than on actual demand decline, Compute performance market moves as the improvements are released, now the industry is waiting for Xeon E5v4 as well new gpu and the new Xeon phi to release orders that's true from the Mac Pro to super computer orders both waiting for Intel/AMD To release that over promised improvement, mostly gpu and mic for compute are delaying new computer servers and workstations orders (the same reason why we don't buy a new mac pro today).
So I consider this specialized market grown as the economy growns and buy as soon new technology is released not in a regular timing as other markets but as soon they can profit from the new technology.
Few specific things are waiting hp Dell and supermicro customers: 22 core Xeon E5v4 and new Xeon Phi knights landing as well the new nVidia and AMD Pro GPU specifically nVidia is almost 2 year delayed since announced Pascal. Ok that is in short term, in mid-long term HPC should move from x86-64 to ARM, PowerPC also Intel should relaunch Itanium At least for HPC the road end for x86 it's visible now.