What a silly idea - but It's not mine.. it's someone elses.
Why not have a cross-platform document library that can be 'open sourced' and thus developed by no-one single vendor as a means of standardizing file formats.
The specification of the file format would become less important - as any changes to the format would be available for all to see. The whole process could be overseen by a few developers repressenting a number of different vendors on a "development council." This would also allow the format to develop logically and smoothly, rather than the archaic method of jumping up to a new format - leaving those using the old one behind.
The idea of a document format becoming obsolete/unreadable always seemed to me to be a problem for the future. However, I recently read that a Service Pack to XP will make some document formats unreadable. A church in America is moving to the Open Document Format in order to provide continuing accessibility of their priests' sermons.
Is it practicable?
Can it be done - well. Hands up if you don't think a group of volunteers can create software than runs 75% of the internet. Doing this is probably more practical than continuing with the current approach. The move to XML is meant to be one that opens up documents - and allows greater cross-format compatibility. I can produce a spreadsheet and a word document using XML. I can integrate and sort things better than I'd ever have thought possible. Freedom of Information is just beginning. Let it continue.