I think people are overestimating some names like Sestak who is still not favored to even win his primary, Cuomo who still hasn't announced a gubernatorial run, and Mark Warner who might have to shift to the middle to win reelection in 2014 which would complicate a primary run.
^^^^ this, though not so much re: Warner. Remember, Bill Clinton was considered from the "moderate" wing of the party in 1992. Also not sure why Gillibrand is getting so much more press than Kolbuchar.
Also, Hillary will turn 69 a week before the 2016 election. Not impossible, but I don't see her seeking the presidency then.