Here's an NCR piece from May, 2012, by the usually well-informed John Allen. After talking to people in Rome, he lists the following names to watch in and around the conclave:
Angelo Scola, 70, Italy
Marc Ouellet, 68, Canada
Leonardo Sandri, 68, Argentina
Peter Turkson, 63, Ghana
Robert Sarah, 66, Guinea
Timothy Dolan, 62, USA
Luis Antonio Tagle, 54, Philippines
It is noteworthy that only four of these eleven names are Europeans. Christoph Cardinal Shoenborn is also frequently mentioned in this context, making him a very reasonable fifth name. On the other hand, Arinze is not named, suggesting that our first instinct -- he is simply to old -- is correct.
The long shots, it should be said, are very long indeed. We have often heard it said that an American will not be elected pope for a very, very long time, and although Dolan is highly regarded -- "a superstar" -- among his colleagues, he is also a relative outsider in Rome.