As always, your emails continue to provide interesting food for thought. Here's a simple one that ought to provoke great thought: "would anyone be interested in a cross-breed between the X and S sensor, say 18mp with ISO ability close to the D3?"
Well, yes, someone would be interested.
Think about it for a moment. In just Fujifilm slide film we've got Sensia 100, Sensia 200, Sensia 400, Velvia 50, Velvia 100, Astia 100F, Velvia 100F, Provia 400x, Provia 100F, and T64. That's today, when nobody is supposedly still using film. Add in negative film, other film producers, black and white films, and specialty films and the list runs over a 100 choices, even ten years into the digital revolution.
Compare that to your DSLR. One choice. If you want the new choice (D3s and its better high ISO) then you have to either give up your old choice (D3) or duplicate the entire camera. Of course, the camera companies are addicted to this "upgrade everything" notion, because it makes their average sale so high and it means you retire camera bodies well before their time. The problem is that fewer and fewer people are interested in such mindless and silly obsolescence as the sensors got competent. The "do I need more than 12mp?" question comes to mind. Indeed, I've been getting a lot of people pondering the "should I really sell my D3 and get a D3s?" question lately. And the answer for more and more people is starting to become "no, the cost of upgrading doesn't justify the image quality benefits."
Consider what would have happened if we had a modular D3: you would have bought a US$2500 body. You would have then bought a US$2500 sensor module (D3 sensor), probably a US$5000 sensor module (D3x sensor), and probably another US$2500 sensor module (D3s sensor). You'd consider that 18mp sensor module that the emailer asked about. I know 20% of you would have bought a US$2500 monochrome (B&W sensor) module. Perhaps 5% of you would have bought a US$2500 IR module (D3 sensor with different filtration). It seems to me that there is more profit and more "lock in" by doing modular than there is doing it the way the companies are currently doing it.
Nikon executives have said several times that they pick "the best sensors available" when they are developing a new camera. But what about the concept of picking "all the available sensors"? In that case we'd also have an 18mp Kodak sensor module choice for our D3 bodies right now. Which would you rather have: the current system where you have two bodies with different sensors, or one body and six sensor module choices? I know where I stand. And I'm pretty sure that I could make the business case where it would actually make more money for Nikon in the long run, too.
It's ironic that a film photographer has more choices of true core "image quality difference" today than does a digital photographer. I'd really have thought it should be the other way around, but we're just not even close. Yes, I know you can process your raw images different or make different camera settings, but it's not quite the same thing. If you don't understand why not, try pushing a D3 image as hard as you do a D3s image, or try converting a Bayer image to monochrome. Changing RGB values is not the same as changing core image quality fundamentals.