Like it or not, fragmentation of the displays has begun.
edit: why so many negative votes? There's a huge difference between simply doubling the resolution in both width and height and completely changing the aspect ratio. It doesn't matter much for apps like an address book but it's going to be annoying to code for a third device with some kinds of apps like games. iPhone and iPhone Retina at 3:2, iPad and iPad@2x at 4:3, iPhone 5@2x at 16:9... if that's not fragmentation I don't know what is.
Thinking "it's not as bad as Android" is no excuse, it's fragmentation anyway.