These days an awful lot of Broadway musicals are based off of movies. There are the ongoing Disney adaptations, for better (The Lion King, Beauty And The Beast) or worse (Looking at you, The Little Mermaid).
Plus there are those based on live action movies like Legally Blonde, Waitress, and The Band's Visit.
It's getting rarer and rarer to see the opposite happen, with a Broadway show leaping to the big screen. No wonder people are so excited about this Wicked news.