The problem with Apple is their seeming unwillingness to promote some of the technologies they develop. I just don't see scientist and engineers running to Apple for compute hardware. It is much easier to build a small cluster with Linux machines, stick them in a closet someplace and connect a Mac to them with a fast pipe. To really compete well as a cluster solution Apple would need a very turn key system that dramatically improves their odds relative to a Linux cluster.
I'm not aware of anything under the hood that would allow this to be seen as anything but a PCI based bridge. It seems like an atypical way to chase performance, and again we haven't seen such a thing actually working. It's just speculation, but I don't know that it would work.
As for these external adapter boxes for GPUs I have a very hard time grasping the wisdom in such hardware. Looking at GUS in that video linked above just had me shaking my head in disapproval. I'm just not sure whom they are trying to reach with such a box. The box takes an external 150+ watt brick to power it which is a mistake right there. Then the box is fairly expensive but yet only handles midrange cards. So while I'm sure such a box will work I just can't see people jumping all over themselves to buy one as you might as well buy a whole PC.
It looks like a fad to me. I expected such a thing to be expensive. A lot of these weird peripherals don't always run on huge margins. External hard drives and things like esata hard drive enclosures tend to rely on relatively low margins, and many of them cut costs with cheap fans and whatever else. Producing such a product with room for margins in a limited volume as I wouldn't expect this to become a mainstream product basically provides what you see here. Such boxes have been around for a bit. It's not an entirely new concept, but they've never caught on. Given the lack of predictability in power draw from one generation to the next, it's easier to just keep a small PC tower up to date.
In any event this is one of the reasons I'm so hot over the idea of an XMac. Apple really needs a low cost desktop that can handle this sort of GPU card. A very much midrange machine. I wouldn't even be bothered if the GPU was soldered right on the motherboard as long as suitable video RAM was supplied. Better yet is an XMac with a soldered in GPU and a PCI Express slot capable of supporting another 200 watts of capability. Such a box could be very capable but low cost as much of the Mac Pro is deleted from the implementation. Well relatively low cost as this would likely still be a $1500 computer.
Trying to visualize this. I like the idea, but i'm not sure they'd do that. The only mac pro that makes very little sense is the low end configuration. That configuration never used to exist. They just increased the price of something similar to the older ones, and put out a new low cost setup at the original price point. The case looks fairly expensive to manufacture, but I don't think that's completely a size thing. The board might be expensive to manufacture. The shell is most likely one that's stayed the same to avoid the design time and expense of a new one.