Totally nailed the refresh on each of these cameras! Now the fun part....
I think the 5DIII is an excellent camera. But I think they failed big time by not having built-in WiFi and removable focus screen. How can they make it better? Resolve these two issues. If it has built in WiFi, have dual CF slots. None of this SD silliness. Built in GPS would be nice. A built-in transmitter/controller for their flash units as someone mentioned earlier. That's an excellent idea. Minimum three groups to control. Five would be better. Better ISO performance and maybe a stop higher on the top end. Maybe an extra stop better in color dynamic range. USB3/Thunderbolt. I don't care much about video... But I think they'll have 4k in it....
The 5DIII is an amazing camera as-is. I think it would take a huge improvement and fantastic new functions for people to upgrade.
I would love to have a 1DX as my workhorse, do-anything camera. The refresh would have to be something out of this world to make make it a worthy update. Built-in WiFi and GPS. An extra stop in upper ISO performance would be nice. But I would rather see SUPERIOR ISO performance from 100 - 50k. Built-in radio transmitter/controller for flash units. Remove the network connector and replace with USB3 and Thunderbolt. Color dynamic range and sharpness that is approaching Medium Format. Again, I couldn't care less about video so... But I think they'll have more and improved video and this will require CFast.
I have a feeling that with the new uber-lenses from Zeiss and Sigma, that they had insider information on Canon's latest. Yes, the Nikon D800(x) can take advantage of these lenses. But that's a tiny tiny market. So in terms of sensor performance, I'm hoping we'll see tech. that will take us into the next 5 -7 years.... Like the previous sensors.
Since it looks like the big MP is not going to happen after all, I think they are going to make the 1DX upgrade a little more suitable for fashion/landscape photographers. The 1DX. Maybe the best overall DSLR in the world. Is really a sports shooter's camera. Sure it's good enough for other uses. But Medium Format is the future for certain pros.
The new Pentax 645Z is currently the in-between camera. Similar AF and ISO performance of the better DSLRs. Better image quality than a top DSLR, but not like the Phase One or Hassy. And certainly cheaper than the Phase One and Hassy. If I was a full time wedding or event photographer, I'd probably go with the Pentax 645Z. Even with the bucks a wedding photographer can make, having a couple of Phase Ones would be crazy money. But two 645Zs is totally doable. And the wedding business is HUGE. If Canon wants to keep and grow their market, they gotta compete with MF.
It's going to be a tough 6 months!!!