That’s what the HiDPI mode suggests, though. If Apple wants to keep the size of UI elements constant (and I’m guessing they don’t want to make them larger) they

That’s what the HiDPI mode suggests, though. If Apple wants to keep the size of UI elements constant (and I’m guessing they don’t want to make them larger) they have to quadruple the resolution. Anything less and they give the user less space to work with. This has not much to do with eyesight. UI elements would stay exactly the same size. That’s the point. It would be like the change from the iPhone 3GS to the iPhone 4.