iOS 64-bit support for unity integrated application

Since 1st of February 2015 Appstore ask for the 64-bit support and be built with the iOS 8 SDK. We had integrated our iOS app with unity and works fine. Currently we are using 32-bit version of unity and we use asset bundles which built from it in our iOS app. According to new regulations we have to change "Architectures" in iOS app to “Standard architectures (armv7, arm64)”. It doesn't support unity parts in the application. As a solution unity suggest to select IL2CPP for Scripting Backend which is available from Unity 4.6.2 . Is there any solution instead of upgrading Unity to latest version ?