I know 3 different people who own a 2010-style Mac Pro at their homes, and we've got a dozen around the office.
Every single one of them is already a rat's nest of cables - Ethernet, monitor, external hard drives, scanners, tablets, keyboards, synths, video editing gizmos - you name it, they've got it plugged in.
So adding one more cable to the mix, to lead from the Mac Pro to a Thunderbolt box, is a total non-issue. Nobody could tell the difference.
This!
I'm one of those Mac Pro owners. What does everyone think comes out of the back of the machine once you fill those PCI slots? Cables, and lots of them.
I've got a digital mixer sitting next to it on my desk, dozens of TRS cables running everywhere, studio monitors, etc, etc, etc... it is a damn rats nest, and the mac is just a small part of the mess. I don't think I'm atypical.
If anything, i hope this stirs development in thunderbolt enclosures so we can get some better choices in the market that don't cost a fortune.
For pro users like me, the main source of anxiety is coming down completely to thunderbolt 2 -- we don't know enough to accurately gauge its performance in the real-world yet. The specs look OK, but who really knows.
I suspect if Apple has made this move, they believe that Thunderbolt 2 is more than ready to handle whatever pro users are going to throw at it.