The versioning system used by Wwise is of the form "YEAR.MAJOR.MINOR.BUILD". Depending on the types of changes in Wwise from one version to another, your projects may not need to be migrated when upgrading to a new version. This is indicatd by two parts of the version: the YEAR.MAJOR and the MINOR version.
We recommend that you always update to the latest minor version. This is always the most stable version since it will contain all existing bugfixes for the corresponding major version. It will also not break your usage of the Wwise SDK and Wwise authoring application (including the Wwise Authoring API). Support for newer platform SDKs are also provided in minor versions, so it will likely be needed for shipping a product for these platforms. The various formats used by Wwise will also remain the same across minor versions. You can expect all of the following to remain compatible:
Soundbanks (no need to regenerate or redeploy)
Work Unit files
Wwise SDK API
Wwise Authoring API (WAAPI)
Because products sharing the same major versions are interchangeable, it is possible to profile a game built against a different minor version of the SDK with the Wwise authoring application. Similarly, banks generated with a different minor version, be it more recent or older, will be compatible within the same major version.