Wouldn't the apps simply have the 1x, 2x, and 3x bundled in. This means the size of apps is going to grow, yet again. Yey...... As for iPhone 5 vs 6. I think legacy apps, games mostly, would be blown up. Anything that uses standard UI widgets would be starched to fill the screen. So in a list view you see more lines, in a text box more characters, etc. I hope that's the solution, at least.