If all of your storyboard localizations stopped working all of a sudden in beta 4 of Xcode 7, then you may be in the same boat as we were. We have a deployment target of 7.0 for one of our apps. As soon as we built it with beta 4, all of the localized strings in main.strings stopped translating, and we would see the non-translated strings.
If you run across this, the workaround is to set your deployment target to 9.0 and then do a "clean" before building and running. You will see all your translated strings. We really want to be able to continue to support users with older versions, and since this particular app isn't using any of the features introduced in iOS 9, we don't want to have to change the deployment target to 9.0.
I submitted a bug report: 22098859.