Source: http://gizmodo.com/5888989/this-is-the-ipad-3-hiding-in-plain-sight
Apple just flashed their new iPad 3 on their Wednesday 7 event invite. You can clearly see the new Retina display in all its glory. Compare the top (invitation) to the bottom (a photo of iPad 2).
The top has a lot more definition. It's clear on the typography in the Wednesday, the spacing in relation to the icon and the edges of the icon itself.
Not only that, but there seems to be NO home button, which explains the mention of the "And touch." in their invitation. How do we know? First, the photo they are showing is on portrait mode. You can't achieve that icon spacing in the landscape mode (which is the only explanation for the lack of home button). Moreover, the icon falls right onto the same water drop that the current iPad 2 falls while in portrait mode. It's clearly a photo of the iPad in portrait mode. And there's no button to be seen.
Additional reporting by Adrian Covert.