Welcome to Current Market Realities 101.
In particular, internal discussions were said to focus around the fact that sales of the high-end workstations to both consumers and enterprises have dropped off so considerably that the Mac Pro is no longer a particularly profitable operation for Apple.
Hardly surprising.
Massive workstations are a little redundant in today's market, which is being driven increasingly by the growing population of Pro-sumers.
In a market where smaller and more efficient can often outperform massive and high-powered (or render the purchase of the latter uneconomical from a bang-for-your buck perspective), we're seeing the inevitable results.
Get rid of the Mac Pro, optimize the hell out of your software, drive innovation in the small form-factor area. Done.