I believe that apple won't change screen sizes or reselutions until the non retina devices are out, apple doesn't want there devices to be fragmented like android. Fragmentation has severely hurt android(googles powering it so it can't die). Also there is no way the ipad 2 could handle it would have to be as powerful as a high end desktop. Also since the screen is bigger you don't need such a high pixle density. After the 320x480 devices are forsaken by apple THEN apple can START to think about another resolution. Apple all ready jumped the gun when they released the iphone 4 without killing the 320x480 devices. What does make sense is that every few years apple will introduce a higher resolution for every device. Also at some point the resolution on every device wil be high enough that your eye won't be able to see the pixles. The retina display is close. A ppi of 356 might be enough to make the pixels un see able. After we actieve pixles that can't be seen, then apple will move on to other aspects of the screen to improve: Color, gamma, viewing angles, etc.