Great news for those with older legacy devices!
Apple Has Some Nice News For Legacy iOS Device Owners -- AppAdvice
Now, if you own an app that is upgraded further than your device could support (e.g. the app only works on iOS 6, but you have an iPad1 that only runs iOS 5), you can now install the older version that can run on your device.
No more do you have apps you bought but can no longer install because it won't run on your iOS version. The AppStore will offer you the chance to put the app on your older iOS device.