Frank is right, the prices will level off (assuming there isn't another global financial crash, which I wouldn't rule out). On the megapixel file size, I don't see any evidence of noticeable better quality as file sizes go up. You just get a bigger file. Just like film, a larger sensor won't give more detail, it only allows bigger enlargements, which in turn will show more detail as the print is larger. There will have to be advances in sensor design to see markedly better image quality in digital cameras, or modifications to the existing setup, like Leica's decision to leave out the anti aliasing filter on their M8 to get sharper images, which has resulted in several unwanted effects.
People are getting somewhat better image quality using Hasselblad digital backs vs DSLR's because they're using Hassy lenses, which are some of the best lenses around. When you rez the files down they look the same. It's exactly the same sensor. Put a Leica R lens on that DSLR and you'll see image quality go up as well, which is why there's a ton of adapters being sold to do just that.
As I mentioned, only Leica has improved the image quality, but you have to do workarounds to fix the problems caused by their "fix".
