As I mentioned before, my roommate, who is from Chicago and has some political connections, seems to think Madigan is set on Governor instead of Senate, and that she doesn't want to go to Washington. Whether it's what happens is another story, but that's what he thinks.
If she wanted the Governorship she would have ran this year and defeated Quinn in the primary when he is as weak as he is now. I think one of the reasons she passed on being Governor is that she was interested in the Senate seat in 2016. Otherwise she would have to hedge her chances that either Quinn is still Governor by 2018 and is termed out or Rauner is Governor and is unpopular which is not guaranteed.