Migration to a new major version is always difficult, and AsyncAPI is no exception, but we want to provide as smooth a transition as possible.
If you are just looking to update your AsyncAPI document, then we suggest you use the AsyncAPI converter. You can do this directly in the CLI with:
asyncapi convert asyncapi.json --output=new_asyncapi.json --target-version=x.x.x
For a detailed read-through about all the changes (non-breaking as well), please do read the release notes for the desired version before hand, as it will give you some more context about the changes.
Here are all the migration guides: