It is a pretty safe bet that whatever will follow the iPad 2 will have a "Retina" screen. 2048 x 1536. Numbers that will be burned into my brain the same way 320x480, 640x960. and 1024x768 are.
But that implies the iPad 3 should also get a camera that is at least 3MP. Why? Because of that screen. 2048x1536 is 3MP! It would be silly to have a camera that wasn't at least that good a resolution, because Apple is going to want to show off that screen. The better the camera, the better the pictures will look.