Convertor plug-ins (that do both read and write) are already available from MS for Word 2000,XP and 2003 so that could speed up docx take-up.

As for SWF, you're not exactly correct. The specification for SWF is freely available provided you sign an agreement before reading it. As part of the agreement you aren't disallowed from 'implementing software that plays the format'. Hence why they're having to use a clean-room approach to create the open source Gnash SWF player.