Hollywood always tend to go for the "hottest stars" to gain box office success.
We live in an age where talent has become secondary to image and hype. Hollywood has always more or less worked that way but it's at a level now that it's never been at before.
If they make this just basically a movie version of the stage musical with all of the lyrics and score intact then it could work but if they try and make it some kind of movie/musical crossover then it will probably be terrible.