I would'nt worry too much about this.
The original will always stand alone as a classic and cant be touched.
Other iconic movies have been remade ie King and I, Willy Wonka (ok not quite up there with Oz) and there popularity, or lack of does'nt dimmish the status of the original.
I dont think if this happens this will be a remake of the Judy Garland musical movie (afterall who's gonna try and take that role and voice on), but maybe based closely on the book. There where quite a few Oz novels written as well, not just one.
I am bit confused by the RAB article as I thought Disney held the rights to the characters-maybe not anymore?