We've purposely not set a public date, as it's a complete rewrite (and we expected to miss even our internal dates), and we've been supplying updates as major milestones are reached.
You can follow the progress
here or find information on becoming a beta tester (which have access to all of the latest beta releases, every couple of weeks)
here.
As of this point we still have several template files that need to be rewritten (login, profile, who's online), changes to the gallery and file manager need finalized, timezone changes, installer rewrite, update to the default settings, and several minor items.
