How come Mamma Mia has become a movie, but Wicked hasn't yet?

i LOVE both musicals mamma mia is older and abba rock.someone did tell me that there would be a wicked movie in few years and this person is like a superfan.mamma mia came to the stage in 1999.but like yourself i cant wait im such a fan ive seen it 3 times in london and was lucky to be in an armature production of wicked in belfast.