First of all, from a "pro" machine I'd expect that it's easy to customize it and upgrade it when the need comes. Since we don't know if it is going to be possible with new Mac Pro or not, let's not go into this topic (if RAM / graphic cards / processors aren't swappable, for me it's just a one big laugh).
Since you are asking, please remember that a lot of photographers are involved in shooting motion nowadays. And also look at a wider spectrum, it's not just photographers and motion guys who were expecting Apple to deliver. But even as as a "mere photographe" when it comes to your desktop needs, you need at least a HD backup rack. This makes it two racks- one for your storage, second for backup. Probably some mass storage / optical 3rd solution for critical projects. speaking of racks- it would be great if the chassis was compatible with server racks. A solution you can put horizontally or vertically depending on the need... and I know guys who would benefit from it greatly due to the amount of hardware they need to work (not neccessarily photographers, but other "pros").
So now we have a mac pro unit with 2-3 additional boxes full of hardware, just to get things started. I won't even go into peripherals that pro users need to attach, like external video cards, pro realtime converters for broadcast applications, etc etc. Oh and yes, each external device usually means it's own power supply, it's own cooling. So, from a PRO standpoint, what are the benefits of this new chassis form? It has a single fan, yeah that's cool, too bad all of the other stuff will need their own fans anyway.
If this thing was MODULAR, detatchable from a bigger module incorporating all of the aforementioned, I would probably like the idea. But the big question remains- will RAM/graphic cards/proccessors be easily accessible and swappable?