just because he can't direct due to other commitments doesnt mean he can't help out in other ways.
dark universe is moving forward because the world of magic is one of dc comics strongest corners. it would be a loss in many ways to carry the dceu onward without that magic corner heavily dedicated.
likely they will use dark universe to usher in elements like doctor fate, shade the changing man, black orchid, and eventually sandman while batman and justice league split their focus between street-level and new gods 4th world style entertainment.