I think most people who use the MacPro (video/image editing people) probably already use external storage because the 4 drive bays from the old MacPro simply are not enough. I'm guessing they analyzed their users produced something that fit users' needs.
With Thunderbolt 2 / USB 3 support, I suspect some enterprising manufacturer will come up with a stackable storage enclosure that matches the design of the Mac Pro. That would meet all your storage requirements while keeping the size down for those who only need the additional performance.
They said it's all external via TB2 (they put in 3 TB2 controllers driving 6 ports)
So cords everywhere then. I do a lot of photo editing an have close to 10 TB storage internal (I repurposed the optical drive bays). I can keep all of my working files internally and only have external drives for archiving and backup and aren't connected all of the time.
Yes. Though considering the volume reduction you can probably get more storage in an external enclosure without going above the footprint of the old Pro.
So cords everywhere then
Sounds like marketing gold for Drobo and Drobo-style solutions.
Seemed like they were really focusing on external expandability via Thunderbolt 2.