Unity 5: Is Streaming Asset Bundles now compatible between unity versions

It looks like there is a lot of great new features coming out in Unity 5.0 but one of the questions I had is does Unity 5 now support streaming asset bundles from earlier unity versions? For example, if I create a asset bundle in Unity 5.0 and then a few minor releases later say Unity 5.5 will I still be able to stream and load the same unchanged asset bundled to a iOS device without having to re-build it? I know there is still cross platform building but thats a different issue.

Will the new ignoretypetreechanges build option solve this problem? If so, what are the cons here?

 

I doubt it - features get improved/replaced/etc, so there's no way to guarantee that a compiled 5.0 asset would work in 5.1.

 

Specifically, the feature below they added should allow old assets to work. The type tree was never included before so the asset bundle was required to use the version compiled on the mobile device. Now that it's included I wonder if you could you use the one provided in the streamed asset build itself.

Unity 5.0 Release Notes:

• AssetBundles: By default include type tree in the assetBundle on all the platform except metro.

 

This was on the user manual before:

Will an AssetBundle built now be usable with future versions of Unity?
AssetBundles can contain a structure called a type tree which allows information about asset types to be understood correctly between different versions of Unity. On desktop platforms, the type tree is included by default but can be disabled by passing the BuildAssetBundleOptions.DisableWriteTypeTree to the BuildAssetBundle function. Webplayers intrinsically rely on the type tree and so it is always included (ie, the DisableWriteTypeTree option has no effect). Type trees are never included for mobile and console asset bundles and so you will need to rebuild these bundles whenever the serialization format changes. This can happen in new versions of Unity. (Except for bugfix releases) It also happens if you add or remove serialized fields in monobehaviour’s that are included in the asset bundle. When loading an AssetBundle Unity will give you an error message if the AssetBundle must be rebuilt.

It would be great to get someone from Unity to verify that it will work on Unity 5 moving forward.

 

In Unity 5.0, we do consider the asset bundle compatibility issue. From 5.0, asset bundle contains type tree by default. So the future version of Unity should be able to read the asset bundle built by Unity 5.0. You may notice the below information in the release notes:

Unity 5.0 Release Notes:

• AssetBundles: By default include type tree in the assetBundle on all the platform except metro.

And ignoretypetreechanges is the option to let you decide if you want to rebuild the asset bundle if only type tree changes, for example you change the public member of the script. It's not compatible with DisableWriteTypetree, if you disable typetree, then you cannot ignore typetree changes.