Apple has sent an invitation for the iPad 3 to journalists for the March 7th event and already there has been one analysis which looked closely at the photo used to find out clues about Apple's next generation tablet.
We tried our best (see below) to emulate the photo created by Apple's marketing team and while we don't have any image editing resource (human or software), there's at least one convincing conclusion that can be derived from this hastily put together experiment.
The iPad in the invitation gaphics is one with a higher resolution (and higher pixel density) than the current one. Note the "e" in the photo we've taken and the "e" in the invite photo.
Check the original invitation file on the Smashwire site and you may notice how the "e" on the iPad 2 has clearly visible jagged edges while the one on the iPad 3 doesn't.