Unity 5 is a major release with, amongst other things, a completely new audio system, the physically-based shader and an updated physics engine as well an API tidy-up. As we’ve introduced so many major improvements, Unity 5 is not, alas, totally backwards compatible. That’s why we’ve introduced a system whereby, when Unity 5 imports a Unity 5-incompatible package, it will try to automatically update that package so that it works with Unity 5. For Unity 5 users, this means the majority of your assets will continue to work smoothly.
Many Asset Store publishers are working hard, using the Unity 5 beta builds, to make their packages compatible with the Unity 5 release. In the event that we encounter Unity 5-incompatible packages, we’ll flag this in the Store. You’re of course welcome to download them anyway and tweak them or work around any minor issues you may encounter.
Unity 5 changes the way the Unity Editor handles Asset Store packages. Therefore, in preparation for its release, we’ve introduced changes to our submission processes, for an easier and friendlier workflow.
If you’re planning to submit assets, you’ll need to read the new Asset Submission Guidelines before uploading them to the Store. Put briefly, you’ll no longer use the downloadable Asset Store Tools to manage your asset and it’s presentation in the Store. Instead, you simply manage your assets using our Package Manager web interface. All you need the Asset Store Tools for is the actual upload process!
Additionally, if you prefer to maintain your package in multiple editions for different versions of Unity, you can now do so. The Asset Store will then automatically display the version of your package that’s relevant to the user in question. Learn more from the guidelines!