This is intriguing

From Slashdot:

According to an MSDN Channel 9 interview with an Office file-format developer, the next version of Microsoft Office (Office 12) will default to newly-developed XML file formats in Word, Excel, and PowerPoint. The new formats will apparently include XML files along with other files (images, etc) inside of a Zip file. Microsoft will also be providing extensive documentation of the new format to the public through MSDN.

Neat-o.