It's finally official. Today the Ecma General Assembly voted almost unanimously to approve the Office Open XML formats as an official Ecma standard. They also voted to submit the standard to ISO for fast track certification. The official press release from Ecma International can be found here: http://www.ecma-international.org/news/PressReleases/PR_TC45_Dec2006.htm

Here's a quote from Jan van den Beld, the Secretary General of Ecma International:

"The broad spectrum of sponsors from the industry and public institutions ensure the creation of an open standard that can create a wide range of possibilities for document processing, archival and interoperability" said Jan van den Beld, Secretary General of Ecma International. "The Open XML standard recognizes the benefit of backward compatibility preservation of the billions of documents that have already been created while enabling new future applications of document technology."

http://blogs.msdn.com/brian_jones/archive/2006/12/07/ecma-standard-376-office-open-xml-formats.aspx