According to an admittedly unreliable source (off to a poor start, I know), the iPad 2 will be 3mm thinner and have a flat back—like the iPod Touch 4G.
According to an anonymous Chinese source, next iPad will be 3mm smaller than the current one.The height of the new iPad will be 239mm and the width will be 186mm.
The LCD screen will remain the same in size and the back face shape of the case will be flat like an iPod touch.
Some leaked photos show that a hole in the lower right of the rear panel is neither a USB connector nor a SD card slot. It is a large, wide-ranged speaker unit covered with metal mesh.
While the source is sketchy at best, the rumors jibe with previous reports, so there may be some validity to it.