Will apps < IOS6.1 work on IOS7

Will apps < IOS6.1 work on IOS7

I have just installed IOS7 Beta 6 on my ipad 2. No problems. Then with
Xcode 4.6(with IOS6.1 SDK), I installed the current version of my app on
my device with IOS7 and it runs and works perfectly. Now, from what I can
gather the UDID or [UIDevice currentDevice].uniqueIdentifier] should no
longer be available on IOS7. My app won't even compile with XCode5 because
of it so does anyone know why my app designed for IOS6.1, using IOS6.1 SDK
still runs on IOS7. Is there some provisioning in IOS7 for this?. When
Apple say that [UIDevice currentDevice].uniqueIdentifier will be no longer
available, do they just mean apps will be rejected if they use it but apps
submitted before the release of IOS7 will still work?
Any help much appreciated
josh