I looked at the list of champions for the past 10 years:
2004: Kuznetsova
2005: Clijsters
2006: Sharapova
2007: Justine Henin
2008: Serena Williams
2009: Clijsters
2010: Clijsters
2011: Stosur
2012: Serena Williams
2013: Serena Williams
Clijsters and Henin have retired, so that eliminates 4 out of 10. I don't see Stosur winning this year (or any other, really).
That leaves Serena, Sharapova, and Kuznetsova. I suspect Svetlana is past her sell-by date, which leaves Sharapova and Serena.
For Maria to win, Serena would have to go out first. Serena has had a shaky year at majors, so it's hard to say what will happen in New York, but she won't lose to Maria.
Azarenka isn't even close to winning a major, and Radwanska will inevitably stumble before the semis. Bouchard is in a shame spiral she can't shake. The only other true contenders are Li Na and Halep. Maybe Kvitova, but she's another one who has trouble in New York.
But despite the weird losses this year, I still think Serena wins it.