Czech Republic site superiphone.cz claims that it got hold of parts from the next-gen iPhone, but they've gone way beyond the analysis of sites like Gizmodo or Vietnamese sites taoviet and tinhte. Specifically, they've taken the screen from a next-gen iPhone, put it under a microscope (how cool is that), and counted the screen's RGB elements to figure out the screen's resolution.
By doing this, the Czech site has confirmed what we've "known" for a couple of months: the next iPhone will have a screen resolution of 960 x 640. This is quadruple the number of pixels on current iPhones, which have a screen resolution of 480 x 320. MacRumors notes this increases the pixel density to 320 dots per inch (dpi), much higher than the Motorola Droid's 265 dpi or Nexus One's 252 dpi.
Because the horizontal and vertical pixel density are exactly double that of current iPhones, scaling apps upward to fit the screen's new resolution will be even easier than the scaling that takes place for the iPad when running iPhone-optimized apps. For apps that do take advantage of the higher resolution (games are the first that come to my mind), the result will be graphics much crisper than anything we've seen before on a device this small.