WordPress 3.1 is running just a little bit behind schedule. But the final release is hopefully not too far away, as the first release candidate (RC1) for WordPress 3.1 is now available.
An RC comes after the beta period and before final release. That means its done.
"We currently have no known issues or bugs to squash. But with tens of millions of users, a variety of configurations, and thousands of plugins, it's possible we've missed something. So if you haven't tested WordPress 3.1 yet, now is the time! Please though, not on your live site unless you're extra adventurous," informs dev team.