I've got an 8CD bootleg of the Get Back sessions which is pretty poor. No wonder it took a couple of attempts to make Let It Be into a half decent album.
There can't be much left in the archives that is worth releasing which didn't make it onto the Anthology set.
I've heard there's easily enough to fill one or two albums. The interesting thing is that Lennon said that the best Beatles stuff was performed in Hamburg and never recorded!