They were meant to start filming in Sept, then it got pushed to October and now they're due to start filming in November. Though work has already started on the sets.
There have been some big clashes behind the scenes, with Erivo wanting the mother to be Black, but the studio hadn't considered a black actress for Nessa. Ultimatums were laid down....
Also, they havn't bothered to pay the royalties for Dorothy's likeness or the ruby slippers and neither will be in the film - where as in the stage version you only see Dorothy's shadow and they shine a red light on the slippers.
Robert DeNiro and Bradley Cooper have both been in to chat with the producers too. Confirmed casting for other roles in a few weeks,