If I was a betting man I'd bet that Brazil is going to host the 2016 Olympics. There has been a lot of buzz surrounding Rio, winning the bid for the summer olympics. It would also be the first time any South American country hosted an olympic event.
I feel Tokyo is out just because a far east country (China) recently hosted it and it would be redundant for Tokyo to host it again since they hosted it in 1964. Madrid has been campaigning hard but haven't heard anything that would indicate they were in the running. They could surprise everyone in the end or be knocked out early.
Chicago is the real contender against Rio. Having Obama physically being there campaigning for Chicago in Copenhagen definitely didn't hurt. But I feel even this won't help America host another olympic event. I only say this becaue we've hosted 8 total olympics and 4 of them being summer olympics.
We shall see though... Announcements will be made this afternoon. Good luck to every country.
To see contender country's logo - click here to my old blog post, Olympic Logos.