If Apple's internal teams have gone final (and that's a big IF) it's not uncommon for a release to still be waiting on:
- notification of changes in code licensed from a vendor or third-party
- a multiple week soak time after the code freeze to discover bugs (eat your own dog food for a while)
- exhaustive documentation of the final changes (both to users and developers)
Even if all of this has been finalized as the rumors indicate, there are still other reasons why a release would be delayed after going final, including:
- Finding the best marketing opportunity to make the introduction (which I know little of).
- Ensuring that one's unfinished hardware has only expected problems and incompatabilities (if any at all).
- Letting the application teams (Final Cut, iWork, iLife, etc) get their work fully compliant before release (the market does have higher expectations for Apple authored apps).
While the Mac rumor sites have been speculating on an early release of Tiger since it was announced last June, I don't think that their rumor-mongering does anything to speed up its release and quite possibly:
- delays distribution of the gold master to developers.
- delays the public announcement until Apple is seen as the one setting the expectations rather than the rumor sites.
- makes open discussion of releases beyond Tiger even more secretive.