Preview at WWDC likely in June, followed by September launch.
Detailed Photo and Video Comparison of iPhone 4S and 'iPhone 5' Front Panels
The blog post contains a number of images and a nearly 7-minute video comparing the two parts, showing that not only is the new part taller than the corresponding iPhone 4S part but it is also 0.1 mm thinner and offers more light transmittance and more scratch resistance than its counterpart.
ETrade Supply has also taken a close look at the home button region of the front panel, showing that the hole for the home button is 0.3 mm smaller in diameter than the hole on the iPhone 4S, while the margin between the bottom of the panel and the bottom of the display area is 2.6 mm shorter, allowing Apple to significantly increase the size of the iPhone's display while only slightly increasing the overall device height.
Comparison of iPhone 4S (left) and "iPhone 5" (right) home button hole diameters
This is not the first time the alleged next-generation iPhone front panel has been caught on video, but this new video and photo comparison does offer the most detailed comparison between the part and the corresponding iPhone 4S part we have seen yet.