The APIs that will be deprecated, but don't have a scheduled shutdown date, include the Code Search API, Diacritize API, Feedburner APIs, Finance API, Power Meter API, Sidewiki API, and Wave API.
Google says that it closely monitors the usage of its APIs as well as the resources necessary to support them. In some of the cases, those APIs that have been targeted for deprecation or shutdown weren't being utilized or the projects they were related to have been shuttered - such is the case with the API for the ill-fated Google Wave. But in other cases, newer APIs have replaced them - that's the case with the book-related APIs that are slated for closure.
Google says that it will suggest alternatives to developers so that they can achieve similar functionality - whether it's pointing to a new version or to a related one. It also says that it has lengthy deprecation periods - as long as 3 years in some cases - in order to help minimize the impact.