Agreed. I am actually very excited to see Beth in this role. I think she could be terrific. I know nothing about this stage version under development. As I understand it, there were many differences between the book and the film. It would make sense that the stage adaptation wouldn't be a direct copy of the film either.
Side note: I've been kinda salty ever since I heard the news that Meryl was playing Dee Dee Allen in the film version of THE PROM. It seems hypocritcal, I know. I realize that film versions of stage shows and vice versa are always going to be different animals. However, besides the fact that Dee Dee Allen was written for and around Beth's talents, I just wish she and other original cast members were going to be seen by a worldwide audience in the film version.
And back to THE DEVIL WEARS PRADA: I feel a nice symmetry to the idea that Beth would be playing a role on stage that Meryl originated on film.