As long as all programs can read a format and it becomes a standard used across the office world who cares if it is open source or proprietary?

I do see the point of moving to a completely XML based approach to document storage though as this would mean the data saved in any application could easily be interpreted by any other application as it would purely be a mix of the data contained in the document and a set of XML markup tags.

It would also mean that even without the original application, data could easily be extracted in the future far down the line. All you would need to do is write a parser to interpret how the markup tags are handled and displayed.