Let’s just now hope that Microsoft won’t try to play games anymore. Besides their rather poor track record at delivering on the ongoing chain of announcements about becoming open and caring about interoperability (as opposed to intraoperability), there are other reasons one might want to take today’s announcement with caution.
One trick they could try and pull for instance would be to put just enough support for ODF to claim that they support it but not enough for people to really use it systematically. They could then tell customers who complain something isn’t working that it’s because ODF isn’t powerful enough, and if they want the full power of Office they need to use OOXML.