Interface Builder in Xcode 6 beta introduces new way for handling different iOS screen sizes. It looks like Apple is preparing developer tools for new devices with various screen sizes and aspect ratios.
If you are not familiar with AutoLayout technique, better learn it today, as the new approach makes use of it in the whole new way. View controllers don't have fixed sizes as it was before, instead you can choose one from nine defined layouts that should work in many different cases.
We can't be sure about new hardware specification, as Apple didn't make any official announcements so far. On the other hand, one thing can be assumed for sure - new devices with different screen sizes are coming!