We can't tell how far away the release is, but in the past by watching the development cycle I think we've had a pretty good idea. Basically when more and more things are fixed, and fewer things are added, we can guess that it's right around the corner.
However, these new "top secret" features throw that whole formula out the window. Those are going to need time to be tested (I presume), so what we may wind up with is a ready-to-release Leopard without the top secret features, followed by buggy seeds with the top secret features. The bugs would be slowly worked out.
In other words, I don't think we can use the old formula this year, until we see what the top secret features are. (It's still interesting to see the new fix/feature ratio in the builds, and it does give us some idea of when it will be ready.)