Not everything is implemented, there still is some stuff left which needs to be restored, so no, they can't release it now.
They already have minor bugs which will be taken care of after the release. The few remaining bugs do damage the game, so why release this mod, when a few more weeks will get it done properly?
They are working on this for something like 2 years now, no need to get sloppy at the end of the development circle.
And how close are we from seeing the content finished?
Y'know, they ought to make a video of their bugs, just for sheer entertainment.