Both the Sydney and Cnet articles suggest specific dates for release (the Sydney articles, I think, is just jumping to conclusions). In any event Mark can say those dates aren't correct, but could still release within the next few months. It doesn't make sense to let the Beta expire without doing something, so that likely sets the outside time limit.
They have said, quite categorically, that they will have something out before Feb 28th, when Beta 4.1 expires. Because they are saying No to a Beta 5 for public preview then we must assume a Version 1.0 release before then. No, I don't have an idea of the date.