Some more thoughts:
Of course camera and back makers depend on sensor makers for their sensors.
On the other hand they can order larger sensors and ask sensor makers to develop what they want.
That is exactly what happened regarding the first full frame 645 sensor from Phase one.
It is not the technical side of the sensor that sets the limits, it is the economics that dictate what will be available.
Progress is not always determined along the lines of logic.
The first volume produced 12 cylinder car was made when the first energy crisis hit the world over 35 years ago.
That company not only survived but sold many cars with 12 cylinder engines although a smaller engine was available as well.
It paved the path for other car manufacturers in Europe to sell 12 cylinder cars as well.
It seems Phase One has set the pace.
In spite of their optimistic estimates for first delivery of new products the 65 MP sensor is about to become reality.
At the current exchange rate this 40 K back will cost 25.000 euro.
That is exactly the price for a 25 MP Sinar back 7 years ago.
Economics will dictate the sale of this back will start in Europe to be followed by the US.
The 645 format with a full size sensor will be the next professional standard for digital MF photography.
Eventually a large company like CZ may start production of lenses for H series cameras.
The designs are ready: an excellent series of newly developed lenses for the Contax 645 is eagerly waiting for a second chance.
Phase has set the pace on paper only. It's a game of marketing one-upmanship I am quite familiar with (I work in advertising). No one is shooting with the P65+ and won't be for some time. However, the Fat Lady at Photokina hasn't sung yet ... which is a few short months away. We haven't heard from Leaf, Sinar or Hasselblad concerning their developments. In fact, that Phase One chose to jump the gun tells me something may be up with the other back makers that forced their hand. I think that is exacly why Hasselblad announced the H3D-II-50 early ... which breaks with their tradition of announcing something and being able to ship it almost immediately.
If the new proprietary 4 channel Kodak technology introduced in the 50 meg H3D-II/50 is utilized in a full 645 sensor, we may see a leap frog in IQ that'll make the P65+ an also ran in less than 6 months ... or not. We don't know because no one has seen anything from any of these backs. Right now it's all talk, and seeing is believing.
I've learned to hold off any pronouncements of superiority until it actually translates into something I can see in prints. And not one of the professional photographers I know is as interested in yet more megs ... nor am I. full 645? Yes, to a degree. Better performance from the cameras and software? Yes. Better high ISO? Yes. Better AF with more AF points? Yes. More megs, No.
My hope is that a full frame 645 back will be offered with larger photo-sites. A 25 to 30 meg 645 with 8.5 Micron pixels is my dream digital back to use with the H camera. And my dream camera right now isn't a vaporware Contax resurrection ... but instead a Focal Plane H camera so I can use all my V lenses including the FE optics or the AF HC glass if I prefer. I am not a fan of the only other focal plane camera still in production and still being improved ... the Mamiya/Phase One. The H camera is so much better in the reality of actual use that it's not even funny. My prior use of the Contax 645 made it a dead man walking after trying the H camera just once. The only other consideration out there IMO is the Hy6 ... but I do not like the Sinar backs and software, nor the Leaf backs which cannot be rotated. Neither system is on my consideration list until the backs improve in terms of opertational aspects.
RE the reality of what you actually get verses a bunch of marketing hype: Here is a sobering comparison of the Phase One P25+ verses the much more expensive P45+ right from the horses mouth:
http://www.captureintegration.com/tests/phase-one/
(see the 2nd test)
This lines up perfectly with my experiences using the lowly CFV. An affordable digital solution that keeps on amazing me with it's file quality. Not a solution for those needing wide angle captures, but for almost anything else it's a stunning performer ... it's my go to system for any portrait assignment, and many smaller commercial jobs. The speedy H3D-II/31 for fashion and events, and the H3D-II/39 mostly using the back on a Rollei Xact-II with Digital APO lenses that no MF lens can equal.
Part of a senior portrait session employing the CFV-II on a 503CW using a 100/3.5 CFi @ f/8: