I have two thoughts on this:
The first is that it doesn't seem that sensor technology has moved much at all in the past seven years. Usability technology has moved, but the sensors, with the notable exception of the 50MP CMOS sensor, are pretty much the same as in the P65+. There's an 80MP version, but that's all I see for movement in sensor tech. (I may well be missing something, but that's why I'm so seriously considering a P65+ as an option.)
The second is that we haven't heard from Leaf yet. I find myself wondering if Phase is not being smarter than some give them credit for in limiting support of old tech in the new camera and backs. It's a very Apple thing to do, throowing out the old tech so it doesn't impede the new. (Of course Apple is a consumer products company, and its support for pro markets has been notoriously weak.) But might it be that Phase One has a strategy to keep support of other systems through Leaf? They already support more of them than Phase does.
This is, of coourse, just idle speculation... or maybe wishful thinking.
DAF
Hi, I also own C645 system with all lenses but the 350 and use two backs on it, both with multishot ability, a Hasselblad CF-39MS and a Sinarback 54H, the CF-39 I also use alternatively to my DSLRs sometimes. What keeps me with the platform are three things:
1. The superb performance of the Zeiss 120mm APO micro lens which I mostly use for multishot
2. The trouble free compatibility of Contax mount backs with Fuji GX-680 which allows me to have movements and even combine them with multishot on my Fuji 5 lens system.
3. The ...JAS adapter(!!!) which allows me to use my Contax glass on my Nikons (there is one for Canon too) with full dedication, which improved the performance of my DSLRs a lot, but also restricted considerably the equipment I have to carry, since one can only add a DSLR body to the bag and have both systems.
If movements and multishot was not in my essentials and it was within my buget, I would have P-65+ as my first choice due to:
A. The size of the image area which would allow my 35mm lens to work as real wide angle,
B. The ability to use the back in "exposure +" 15mp mode with 2 stops of sensitivity gain.
If my budget was restricted to spend as low as possible, I would either look for an old 22mp Kodak sensor back which IMO (and many others) have superb image quality (the famous "fat pixel magic") but are a bit more prone to moire issues, or look for a Dalsa 33mp back which are known for their superb color and accuracy. As you previously said, Image quality hasn't changed with CCD backs during the last decade... only sensor size and pixel count has...