Repair Labs Blog next to the casing for the current model. While both look similar, the iPad 3 casing is a bit thicker to accommodate what is expected to believe a larger battery, re-designed logic board, new cameras and an updated display on the upcoming model. Speaking of the display, The Verge says it will be a Retina display with resolution of 2048 x 1536 and the iPad 3's body will be one millimeter thicker than the body of the iPad 2.
The letters on the picture of the two casings show differences between the one for the Apple iPad 2 (L) and the one for the Apple iPad 3 (R). "A" shows the difference mounts between the two for the logic board. The re-designed logic board requires less room on the newer tablet and that allows for a larger battery on the iPad 3, which is noted with letter "B". "C" stands for camera and the new model is expected to have a new shooter. The different mount for the screen at "D" dovetails with talk of a new (hopefully higher resolution) display for the next Apple iPad.
So when might we see the launch of the Apple iPad 3? Considering that this year is a leap year, there will be a 29th of February. This year, the extra day falls on a Wednesday which is the day that the first two iPads were introduced on. Last year, the Apple iPad 2 was introduced on March 2nd and launched on March 11th. The Verge daydreams about having the latest Apple tablet announced on February 29th and launched on the weekend of March 9th, 2012.
source: TheVerge, RepairLabsBlog via electronista