The iPad is used at a greater distance than the iPhone; 260 DPI *is* a retina display.
I’ve seen a number of articles like this, suggesting that Apple is going to double the resolution of the display in the next iPad because of some of the graphics they’ve found digging around in the iOS. The articles say that while 260 DPI is good, it’s “not quite a ‘Retina’ display.” That’s rubbish. The typical distance between the iPad and your eyes is greater than when you’re using the iPhone. The difference between the (rumored) resolution of the iPad 2 and the iPhone 4 is just 25%, so if you hold the iPhone at a foot and the iPad at 18 inches, the iPad will have a *higher* apparent resolution.