MultiAssetScaler 1.1 released 02.18.2015 now Support Unity 5. The plugin allows for scene assets to be scaled up/down in size by modifying the scale factor of the imported models. Once the scale factor has been modified the tool will then re-position the models so the scene looks the same as the original.
A forum will be created on the Unity site once the asset has been released.
Check out the youtube videos below.