From Brian Jones blog:
“Today we are announcing the creation of the Open XML Translator project that will help translate between the Office Open XML formats and the OpenDocument format. …”
Microsoft is supporting a Translator project which is available on Sourceforge (http://sourceforge.net/projects/odf-converter) to convert Office Open XML Formats to the OpenDocument format. It will also contain the possibility to open from and save to the OpenDocument format from within Word.