I am constantly dismayed at the lack of understanding of what constitutes a professional machine here, and can only put it down to most people commenting are not professional users and are criticising a machine gendre they have little use for or knowledge of...
Lets be clear the development of the existing lineup without the MacPro could very happily suffice for Apple without all the costly proapps hassle and especially considering the other half of the commercial world population that are now starting to become a profitable open market for Apple which would be far easier to market with easy to use none critical but highly integrated applications promoting further inbuilt Apple sales.
When it comes to providing machines for the much smaller but also diversely specialised Professional market then we have to think in terms of what hardware is most suited to the choice of software needed and today Adobe leads the greater part of that creative market, nearly all most employed top Professional software requirements can cost equal too or more than the machine they are run on making productivity the name of the game, Apple have spent years trying to run and match the MacPro with MacOS up against the PC/windows fraternity and today they have all but lost that initiative.
The only folk I know of that haven't yet migrated their Professorial (money making businesses) to PCs are only dithering in decision that they know they will have to eventually make.
That is not to say that many lighter professional individuals will find the iMac a quite suitable machine for their needs and will happily stay in the Mac camp, but studio use invariably needs the heavey lifting processing of ever more capable machines to maintain their commercial advantage and in the abscence to a competing MacPro line they have had to swop allegence by force of circumstance, and whats more sophisticated PCs like the ultimately customisable Maingear CS5.5 setup
on Windows OS is a very impressive markup at a simular build cost to a relatively inferior MacPro and somewhat lacking MacOS today.
In order for Apple to continue with the Macpro then this is the target market for such a machine to compete in, or change direction and like they withdrew from the server market Apple can redesign rename and re-purpose their flagship for a more lucrative semi professional market and by that I mean the independent SOHO creative artist market.
to that end I would propose a compact mini water cooled i7 based 22nm Ivybridge machine as the twin Zeon board is getting on and well past its SBD where the i7 based cpu range apart from being more cost effective is matching up on performance too and the future rummers are of 16/20 core Intel single processors to come in the 2011 socket,
As with the trend all SATA mechanical and opticle drives are outgoing and Apple do not and neither should design a retro machine, but PCIe mini format would provide all the future SSD and the very good news of the rummered return to nVidea GPU processing cards in the Mac.
this small but quite customisable MacX with TB would be radical but then thats Apple all over.
And what does the future hold well ARM A15 full size quad core parallel processing chips are a couple of years down the road yet but... nVidea Maximus
for studio professionals though who moving into the future need lossless 4k 3D editing rendering and low audio latency multiple plugins then Apple would have to compete with the top end of new developments and when a new board/CPU comes out for a tower its easy to swop out rather than have to buy a new machine to upgrade, then theres the built in hot swop libruary HDs and bluray for proofs not to mention 4K plasma screen drives, and full size multi-touch control tables all fully supported in windows.
Although I have been a proud owner of the MacPro for over eight years I too think its the end of the line for that particular niche machine, but that certainly doesn't mean the end of Apple-mac.