Once Office is gone, Linux on the desktop is in. Office is the reason why businesses need windows on client, and exchange servers on the back end. Game over man, game over.
Why do you need Exchange Server on the back end to handle office? Office works fine on a standalone PC, SOHO users just have it running on a single PC or use windows shares (without a domain controller) to share documents. Office documents can be stored on any shared file system and sent/received by any email system. So exchange server is not needed to support office.