I think the best advice given here is to make sure you get what you need for your shooting style and situation. Cameras are now getting so good that it doesn't matter what you shoot, the image quality is there and the pixels are there, from the Canon 1D(s)3 series, which includes the new 5D2, and the Nikon D3 series forward, except that Nikon just now got with the pixel game. Given the cameras that have come out in the last year to year and a half, you're good as far as image quality and extra pixels to crop or pack together in A3 sized prints so that most any noise is not an issue when printed. I printed a few "noisy" images in shadow areas after some Lightroom and PS noise removal, and I mean some really quick hit the button move the slider stuff, and at 12x18, I couldn't see any noise, especially in portrait stuff. They do have a different look, but it's all good it seems these days. No one seems to be bitching about processed and printed images anyway.
Again, the best advice given here is to pick the camera that best suits your needs, and just go with it. If you can wait six months, it will be interesting to see what Canon will offer in spring, since I doubt lots of people are going to fork out 8K US for the 1DS3 when they can get 3 5DMKIIs for less money. I know first handed that pro photographers in Manhattan choose several 5Ds over the DsMKII when the 5D hit the market for quality vs price point. Point being, Canon MUST come out with something that will blow us away to get 8K for a camera ever again. Although tests I've sen recently put the general image quality of the 1DS3 ever so slightly above the 5D2, the price isn't justified anymore for the 1DS3 (unless you just have to have the best sealing).
As Bernard said, the 5D2 is a landmark camera in more ways than the 5D was because for one, you get 21MP and motion, quality motion. I really don't know where cameras in the 35mm format can go from here, except better and better dynamic range and lower, high ISO noise. But again, the leaps in quality are getting so close together now, it's beginning to be a non issue. Functionality, such as ergonomics, FPS, etc. are the thing that matter most now. Maybe they will put CAD and CGI programs embedded in the cameras so you can automatically change the model's, car's, etc. ligihting and shadow pattern and color?
Come to think of it, I haven't wet swabbed my 1DS3 since I bought it six months ago, and the images are clean. Just a point showing how good cameras are getting all around. It is the day of the digital for sure.