Are cached asset bundles persistent when application updates?

Hi, I'm developing a project for iOS and Android. I would like to use [WWW.LoadFromCacheOrDownload][1] to download asset bundles. This should cache asset bundles between sessions so that users won't have to download every time they run the app. What happens if I release an update for my app? Will users have to download asset bundles all over again? Thanks [1]: http://docs.unity3d.com/Documentation/ScriptReference/WWW.LoadFromCacheOrDownload.html