I really really wish they would fix USB3 in the IQ's, I agree totally. Only today I had to run off to apple to get firewire adapter for thunderbolt to tether. Minor annoyance, but one none the less.
My personal OPINION, is they screwed something in the engineering which has made it either really hard, or impossible to enable USB3 in a current back without some kind of hardware change.
This is based on nothing more than past experience as an embedded systems designer/firmware developer. That is my supposition on why its taken this long, but it is, at best, a guess.
But other than that, I LOVE my IQ back, without reservation. Are there somethings I'd like better, sure. (like better liveview, wouldn't we all). But frankly what is there no is so far ahead of what else there was in MF before, it is still very good. I have only being doing it (MF digital) 1 year now, but I am utterly hooked on the technical camera. Right tool for the job and all that.
Phase AF- Sits in the draw. When I want an SLR, I use the 1Dx. Biggest complaint. Focuses as speed-of-snail.