Preview at WWDC likely in June, followed by September launch.
Photos of Partially Assembled Next-Generation iPhone Show Component Layout, Thickness Comparison
Sohu now posts (via Nowhereelse.fr) a new set of photos of parts for the next iPhone, including a photo showing a number of components placed into their proper positions within the rear shell. The flex cable housing the external buttons, the SIM tray, and dock connector/headphone jack flex cable can all be seen in the photo. Much of the remainder of the interior of the device will be taken up by the battery and logic board, which would be installed on the left and right sides respectively.
Parts repair firm iResQ published a set of photos with a similar theme earlier this week, installing the bare components into their proper positions in the rear shell.
The photos from Sohu also show an assembled front panel for the next-generation iPhone placed onto this partially assembled rear shell, giving a good look at the overall appearance of the device. Photos of a similar assembly appeared a month ago, but these new photos offer a fresh perspective on the complete device, comparing it to the iPhone 4 and 3GS and giving a good look at the comparative thickness of the three devices.
One final tidbit comes from iLab Factory, which posts a photo of the silver rear shell of the white next-generation iPhone but with black strips at the top and bottom for the antennas. All other photos of the rear shell from the white device seen to date have contained white strips.