From an interview on March 9, 2008 with Gregory Maguire:
According to Maguire, there are plans to bring out a film version of “Wicked” in the year 2014. “That’s the 10-year anniversary of its Broadway debut,” he said, “which is exactly what happened when the play ‘Chicago’ came out as a film a few years ago. Since ‘Wicked’ is breaking attendance records all over the world, there’s no need to rush a film out now.”
And another interview conducted a few days before the first:
Q: What was your reaction when they first talked to you about your novel Wicked being made into a musical? Has anyone ever asked you about it being made into a film?
GM: Within 10 days of the book's publication in the US, I started to get film offers. I had three and a half years' worth of film scripts, each one of which was worse than the one before!
When that interest began to erode (Harry Potter and Lord of the Rings hadn't come out yet) and the notion of a Broadway play came up instead, really in my heart of hearts I just thought [*singing and leaping from his chair*] 'Broadway!'. What was not to love about it?
There will eventually be a film of Wicked the musical but probably not for four or five years.
It will definitely win multiple awards. I'm thinking costume design and musical score most likely.