If you're planning to change to a different ecosystem of terminology, navigation and applications, it's best to start out small and gradual. Pick the low hanging fruit first to convert. Once, the migration has successfully occurred and the situation has stabilized, then you can move on to the next area in your business to convert.
The IT Director in this example was very thorough and conservative enough in his approach to organizational change, which allowed him and his staff to appropriately deal with any speed bumps in their first launch. He left the Design and Finance departments to deal with last, because they dealt with specialty applications which couldn't be easily converted to Google apps.
I have recommendations for this IT Director. If the intention is to get off the XP platform to a platform and ecosystem which reduces the total cost ownership (TCO) of maintaining and running applications and infrastructure, then he can transition the Design and Finance departments to Ubuntu Studio or Linux Mint distributions. He could have the Design team learn Scribus, Blender, Inkscape and Gimp for design work and publishing on the Ubuntu Studio OS. In the
meantime, Finance could use LibreOffice Calc from the LibreOffice suite as a replacement for Excel. (See my related post on transitioning to LibreOffice.) Keep in mind that should they later transition to a Chromebook Pixel, they can use LibreOffice Calc from the cloud via rollapp services.