A new full-frame pro camera generation is hatched from Nikon, the D4. For those with six thousand bucks to blow and the gumption to carry a camera this size, it should be highly satisfactory! 16 megapixels full frame, up to 12.800 ISO plus four extended settings! Ten frames per second with autofocus tracking! Und so weiter as our Germanic friends say.
For a long while now, the D3S has been the king of low-light performance. But there has not been a camera of reasonable size and weight which has had similar performance. And the D4 does not correct this, this chunk could stop a raging bull. It would be nice if/when somebody does come up with something. The Canon 5D2 is getting long in the tooth (over three years), and it's about two or even three stops behind in high-ISO quality.
For both Canon and Nikon, for the first decade of their professional cameras, you had to choose between speed and highest picture quality. But with the D4 and the new equivalent Canon (1D IV) both at 16MP and very speedy indeed, I daresay this is a thing of the past. There's a chance both Canon and Nikon will come out with a 30MP full frame model later, but I do think that'll be a specialist tool, demanding the very best (expensive, big, heavy) lenses to even show a meaningful difference.
Just lookkit this monster...