Here's my 2 cents...
Yes, there will be a new Mac Pro. Why? Apple is spending valuable time and resources and Final Cut Pro X...after their bungled launch of the new app. It is the only Apple Pro app that has a 30 day free trial that I know of currently. Final Cut Pro X is a CPU hog. The more cores it has to use, the faster it'll render. iMacs can "run" Final Cut Pro X, but that's like saying a Honda Accord can race in the Indianapolis 500. It can, but...
So, why the long delay since the last release? Well, 4 thoughts come to mind.
The first is Blu Ray. We all in the video production world expected that Blu Ray burners would replace DVD burners in the new Mac Pros. Steve Jobs' description of Blu Ray licensing made it clear what happened with this version of the Mac Pro.
The second thought is Intel. While the Blu Ray licensing issue stalled an incremental release of a new Mac Pro, the delay also revealed that Intel didn't have a new CPU to make a compelling new Mac Pro for sale either. So another reason not releasing a mediocre incremental improvement Mac Pro. Side note - heat is one of the biggest reasons if not the biggest that has stalled/slowed down the GHz growth in CPU development.
The third thought is the argument that many of the old "Pros" of Final Cut Pro have against Final Cut Pro X - "Apple dumbed down the pro app to sell it to the masses..."
And the fourth thought is Thunderbolt...
While I don't know for sure what reasons Apple had for not releasing any incremental improvements to the Mac Pro, I do believe, that during this extended period of time without a new Mac Pro model, technology has grown beyond what the Mac Pros used to cater to meaning the Mac Pros were built for "power" users like programmers, researchers, 3D renderers, video production, audio production, etc.
However, each of these power users have very different uses for the Mac Pro and spend additional time and resources to customize the Mac Pro to meet their specific needs.
What Apple has learned from their success with the iPod, iPhone, iPad, iOS and their "failure" with Final Cut Pro X, is that the power user is a consumer, too, and expects innovation out-of-the-box from Apple.
Thunderbolt is that innovation.
Why is another cable/plug such an innovation?
Yes, it's bandwidth surpasses USB, Firewire and Sata II. Yes, Apple combined it's video cable and power cable with the data cable. OOOOooo, I can keep my USB keyboard plugged into my Apple Display and attach my MacBook Pro to it with just one cable now. My Apple Display is now my laptop dock and Apple has found another way to reduce cable clutter. Yay.
But, let's go back to Thunderbolt is faster than Sata II.
My internal hard drives are connected to the motherboard by Sata II. That's 6 Gb/s.
Thunderbolt is 10 Gb/s...and it's an external connector...a 3 meter cable connection.
For the first time in history, my external hard drive will operate on a faster connection (bus) than my internal hard drives.
The traditional PC case is designed around the concept that the hard drives have to be close to the motherboard due to cable length restrictions of PATA and SATA.
Now those restrictions are gone...
So, the Mac Pro is a big metal tower. Why? When you open the side panel, you see a big empty space. For what? Air flow and heat dissipation.
Heat is generated by the CPU, the video card GPUs, hard drives and power supply.
Now, Apple has successfully made a fanless computer called the iMac. And Apple is rumored to be making an Apple TV that's a display.
Ever wonder why Apple didn't add an option for an extra hard drive slot in the iMac? Space is one consideration, but the additional heat is probably the bigger factor since there are no fans in the iMac.
Ever wonder why Apple didn't put the faster CPUs into the smaller display iMacs? heat dissipation. There's more surface area on the 27" iMac to dissipate the additional heat of the faster CPU.
I wonder just how much less heat there will be if Apple were able to separate the hard drives and the power supply from iMac display and made them an external attachment connected by a single Thunderbolt cable.
I wonder, if by doing so, Apple would be able to put a faster CPU (XEON chip) and a faster video card into that display.
I wonder if Apple's rumored Apple TV with it's rumored screen sizes of 32" to 55" would help allow for a faster CPU and video card in fanless computer display.
I wonder if Apple instead of doing all this for an iMac would make the new Mac Pro a revolution in case design.
I know as a video editor, I would love to be able to edit on a 55" display and I would love to be able to attach my hard drive array(s) to it with just a single cable...that would daisy chain to my other 55" display(s) without having giant Mac Pros cluttering up my small studio. After all, I'm a video production studio, not a data center.
Apple has got a brilliant industrial designer named Jonathan Ive. And if I can think of something like this based on what I see publicly, what is he thinking...